Remove references to openssl from building on macOS docs.

[bzbarsky-apple]

We are now defaulting to boringssl (which is a submodule), so no need to mess with openssl.

[github-actions]

PR #24952: Size comparison from 11c0cdf to 0b80b61

Full report (5 builds for cc32xx, linux, qpg)

platform	target	config	section	11c0cdf	0b80b61	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	640233	640233	0	0.0
			(read/write)	204084	204084	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197488	197488	0	0.0
			.comment	194	194	0	0.0
			.data	1476	1476	0	0.0
			.debug_abbrev	928439	928439	0	0.0
			.debug_aranges	87352	87352	0	0.0
			.debug_frame	299840	299840	0	0.0
			.debug_info	20194395	20194395	0	0.0
			.debug_line	2649797	2649797	0	0.0
			.debug_loc	2785922	2785922	0	0.0
			.debug_ranges	280720	280720	0	0.0
			.debug_str	3001474	3001474	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	105585	105585	0	0.0
			.shstrtab	232	232	0	0.0
			.stab	204	204	0	0.0
			.stabstr	441	441	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	375840	375840	0	0.0
			.symtab	255856	255856	0	0.0
			.text	532524	532524	0	0.0
linux	chip-tool-ipv6only	arm64	(read only)	11997396	11997396	0	0.0
			(read/write)	727720	727720	0	0.0
			.bss	34248	34248	0	0.0
			.data	3008	3008	0	0.0
			.data.rel.ro	670008	670008	0	0.0
			.dynamic	560	560	0	0.0
			.got	15256	15256	0	0.0
			.init	24	24	0	0.0
			.init_array	208	208	0	0.0
			.rodata	583220	583220	0	0.0
			.text	9687412	9687412	0	0.0
	thermostat-no-ble	arm64	(read only)	2510292	2510292	0	0.0
			(read/write)	145224	145224	0	0.0
			.bss	56456	56456	0	0.0
			.data	1824	1824	0	0.0
			.data.rel.ro	77496	77496	0	0.0
			.dynamic	560	560	0	0.0
			.got	5408	5408	0	0.0
			.init	24	24	0	0.0
			.init_array	432	432	0	0.0
			.rodata	151040	151040	0	0.0
			.text	2097280	2097280	0	0.0
qpg	lighting-app	qpg6105+debug	(read/write)	1148688	1148688	0	0.0
			.bss	99876	99876	0	0.0
			.data	848	848	0	0.0
			.text	595788	595788	0	0.0
	lock-app	qpg6105+debug	(read/write)	1116736	1116736	0	0.0
			.bss	96396	96396	0	0.0
			.data	860	860	0	0.0
			.text	563832	563832	0	0.0

[github-actions]

PR #24952: Size comparison from 3a8096d to 0cb13a6

Decreases (1 build for cc32xx)

platform	target	config	section	3a8096d	0cb13a6	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	20194396	20194394	-2	-0.0

Full report (1 build for cc32xx)

platform	target	config	section	3a8096d	0cb13a6	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	640233	640233	0	0.0
			(read/write)	204084	204084	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197488	197488	0	0.0
			.comment	194	194	0	0.0
			.data	1476	1476	0	0.0
			.debug_abbrev	928439	928439	0	0.0
			.debug_aranges	87352	87352	0	0.0
			.debug_frame	299840	299840	0	0.0
			.debug_info	20194396	20194394	-2	-0.0
			.debug_line	2649797	2649797	0	0.0
			.debug_loc	2785922	2785922	0	0.0
			.debug_ranges	280720	280720	0	0.0
			.debug_str	3001474	3001474	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	105585	105585	0	0.0
			.shstrtab	232	232	0	0.0
			.stab	204	204	0	0.0
			.stabstr	441	441	0	0.0
			.stack	2048	2048	0	0.0
			.strtab	375840	375840	0	0.0
			.symtab	255856	255856	0	0.0
			.text	532524	532524	0	0.0