Fix Mbed docker image for CI

[ATmobica]

Problem

The Mbed OS docker image included the PW_ENVIRONMENT_ROOT definition which causes that the default .environment directory is not created when we used the Mbed OS docker image directly. The CI workflow scripts refer to the .environment directory and that causes the fault.
PW_ENVIRONMENT_ROOT definition is redundant so we can remove it.

The issue is identified during #10619 and was caused by #9432 PR.

Change overview

Remove PW_ENVIRONMENT_ROOT env from Mbed docker image

Testing

Locally build and tested

[github-actions]

PR #10645: Size comparison from 4c7f664 to ae33f7a

8 builds (for k32w, p6, qpg, telink)

platform	target	config	section	4c7f664	ae33f7a	change	% change
k32w	lock-app	k32w061+debug	.bss	69052	69052	0	0.0
			.data	1864	1864	0	0.0
			.text	515520	515520	0	0.0
	shell	k32w061+debug	.bss	55080	55080	0	0.0
			.data	672	672	0	0.0
			.text	357332	357332	0	0.0
	lighting-app	k32w061+se05x+release	.bss	78576	78576	0	0.0
			.data	1900	1900	0	0.0
			.text	614304	614304	0	0.0
p6	lock-app	default	.bss	68216	68216	0	0.0
			.data	2416	2416	0	0.0
			.heap	962712	962712	0	0.0
			.text	1126624	1126624	0	0.0
qpg	lighting-app	qpg6100+debug	.bss	53552	53552	0	0.0
			.data	996	996	0	0.0
			.text	486616	486616	0	0.0
	lock-app	qpg6100+debug	.bss	52488	52488	0	0.0
			.data	952	952	0	0.0
			.text	462684	462684	0	0.0
	persistent-storage-app	qpg6100+debug	.bss	17778	17778	0	0.0
			.data	280	280	0	0.0
			.text	102704	102704	0	0.0
telink	lighting-app	tlsr9518adk80d	bss	71000	71000	0	0.0
			noinit	33216	33216	0	0.0
			text	458304	458304	0	0.0

14 builds (for efr32, linux, mbed)

platform	target	config	section	4c7f664	ae33f7a	change	% change
efr32	lighting-app	BRD4161A	.bss	118036	118036	0	0.0
			.data	1800	1800	0	0.0
			.text	782944	782944	0	0.0
	lock-app	BRD4161A	.bss	115892	115892	0	0.0
			.data	1760	1760	0	0.0
			.text	762088	762088	0	0.0
	window-app	BRD4161A	.bss	116212	116212	0	0.0
			.data	1764	1764	0	0.0
			.text	763012	763012	0	0.0
	lighting-app	BRD4161A+rpc	.bss	131364	131364	0	0.0
			.data	1852	1852	0	0.0
			.text	762700	762700	0	0.0
linux	all-clusters-app	debug	.bss	52176	52176	0	0.0
			.data	978	978	0	0.0
			.data.rel.ro	58688	58688	0	0.0
			.dynamic	592	592	0	0.0
			.got	4072	4072	0	0.0
			.init	27	27	0	0.0
			.init_array	512	512	0	0.0
			.rodata	136373	136373	0	0.0
			.text	1345186	1345186	0	0.0
	chip-tool	debug	.bss	17552	17552	0	0.0
			.data	1584	1584	0	0.0
			.data.rel.ro	86192	86192	0	0.0
			.dynamic	592	592	0	0.0
			.got	4344	4344	0	0.0
			.init	27	27	0	0.0
			.init_array	416	416	0	0.0
			.rodata	178892	178892	0	0.0
			.text	2859941	2859941	0	0.0
	ota-provider-app	debug	.bss	37472	37472	0	0.0
			.data	752	752	0	0.0
			.data.rel.ro	23176	23176	0	0.0
			.dynamic	592	592	0	0.0
			.got	4008	4008	0	0.0
			.init	27	27	0	0.0
			.init_array	440	440	0	0.0
			.rodata	110056	110056	0	0.0
			.text	1010594	1010594	0	0.0
	ota-requestor-app	debug	.bss	205728	205728	0	0.0
			.data	752	752	0	0.0
			.data.rel.ro	24488	24488	0	0.0
			.dynamic	592	592	0	0.0
			.got	4136	4136	0	0.0
			.init	27	27	0	0.0
			.init_array	512	512	0	0.0
			.rodata	128744	128744	0	0.0
			.text	1130130	1130130	0	0.0
	shell	debug	.bss	16072	16072	0	0.0
			.data	242	242	0	0.0
			.data.rel.ro	35120	35120	0	0.0
			.dynamic	592	592	0	0.0
			.got	3496	3496	0	0.0
			.init	27	27	0	0.0
			.init_array	336	336	0	0.0
			.rodata	71855	71855	0	0.0
			.text	569858	569858	0	0.0
	tv-app	debug	.bss	216400	216400	0	0.0
			.data	2032	2032	0	0.0
			.data.rel.ro	55872	55872	0	0.0
			.dynamic	592	592	0	0.0
			.got	4400	4400	0	0.0
			.init	27	27	0	0.0
			.init_array	608	608	0	0.0
			.rodata	152264	152264	0	0.0
			.text	1464706	1464706	0	0.0
	bridge-app	debug+rpc	.bss	52912	52912	0	0.0
			.data	976	976	0	0.0
			.data.rel.ro	25784	25784	0	0.0
			.dynamic	592	592	0	0.0
			.got	3944	3944	0	0.0
			.init	27	27	0	0.0
			.init_array	400	400	0	0.0
			.rodata	110644	110644	0	0.0
			.text	1052629	1052629	0	0.0
	lighting-app	debug+rpc	.bss	42232	42232	0	0.0
			.data	1106	1106	0	0.0
			.data.rel.ro	52496	52496	0	0.0
			.dynamic	608	608	0	0.0
			.got	4104	4104	0	0.0
			.init	27	27	0	0.0
			.init_array	528	528	0	0.0
			.rodata	127857	127857	0	0.0
			.text	1253906	1253906	0	0.0
mbed	lighting-app	CY8CPROTO_062_4343W+release	.bss	172164	172164	0	0.0
			.data	5464	5464	0	0.0
			.heap	858816	858816	0	0.0
			.text	1219944	1219944	0	0.0
	lock-app	CY8CPROTO_062_4343W+release	.bss	171084	171084	0	0.0
			.data	5432	5432	0	0.0
			.heap	859928	859928	0	0.0
			.text	1197840	1197840	0	0.0

2 builds (for esp32)

platform	target	config	section	4c7f664	ae33f7a	change	% change
esp32	all-clusters-app	c3devkit	.dram0.bss	60296	60296	0	0.0
			.dram0.data	16192	16192	0	0.0
			.flash.rodata	199008	199008	0	0.0
			.flash.text	872638	872638	0	0.0
			.iram0.text	57330	57330	0	0.0
		m5stack	.dram0.bss	62792	62792	0	0.0
			.dram0.data	32084	32084	0	0.0
			.flash.rodata	207432	207432	0	0.0
			.flash.text	902739	902739	0	0.0
			.iram0.text	125115	125115	0	0.0

10 builds (for nrfconnect)

platform	target	config	section	4c7f664	ae33f7a	change	% change
nrfconnect	lighting-app	nrf52840dk_nrf52840	bss	112332	112332	0	0.0
			rodata	97776	97776	0	0.0
			text	577652	577652	0	0.0
	lock-app	nrf52840dk_nrf52840	bss	111348	111348	0	0.0
			rodata	94112	94112	0	0.0
			text	559152	559152	0	0.0
	pigweed-app	nrf52840dk_nrf52840	bss	51772	51772	0	0.0
			rodata	45772	45772	0	0.0
			text	339392	339392	0	0.0
	pump-app	nrf52840dk_nrf52840	bss	111416	111416	0	0.0
			rodata	95092	95092	0	0.0
			text	562308	562308	0	0.0
	pump-controller-app	nrf52840dk_nrf52840	bss	111356	111356	0	0.0
			rodata	94172	94172	0	0.0
			text	558944	558944	0	0.0
	shell	nrf52840dk_nrf52840	bss	107316	107316	0	0.0
			rodata	71640	71640	0	0.0
			text	519032	519032	0	0.0
	lighting-app	nrf52840dk_nrf52840+rpc	bss	108572	108572	0	0.0
			rodata	88560	88560	0	0.0
			text	550856	550856	0	0.0
		nrf5340dk_nrf5340_cpuapp	bss	113704	113704	0	0.0
			rodata	93016	93016	0	0.0
			text	507116	507116	0	0.0
	lock-app	nrf5340dk_nrf5340_cpuapp	bss	112720	112720	0	0.0
			rodata	89372	89372	0	0.0
			text	488612	488612	0	0.0
	shell	nrf5340dk_nrf5340_cpuapp	bss	108300	108300	0	0.0
			rodata	66284	66284	0	0.0
			text	439632	439632	0	0.0