Disable the shared-reviwers-signify group for now.

[bzbarsky-apple]

Due to dropseed/pullapprove#71 it's causing PRs to land with an insufficient number of reviews.

[github-actions]

PR #25627: Size comparison from be24854 to 3d754d0

Increases (1 build for cc32xx)

platform	target	config	section	be24854	3d754d0	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL	.debug_info	20275630	20275631	1	0.0

Full report (1 build for cc32xx)

platform	target	config	section	be24854	3d754d0	change	% change
cc32xx	lock	CC3235SF_LAUNCHXL		0	0	0	0.0
			(read only)	645097	645097	0	0.0
			(read/write)	203848	203848	0	0.0
			.ARM.attributes	44	44	0	0.0
			.ARM.exidx	8	8	0	0.0
			.bss	197248	197248	0	0.0
			.comment	194	194	0	0.0
			.data	1480	1480	0	0.0
			.debug_abbrev	930293	930293	0	0.0
			.debug_aranges	87384	87384	0	0.0
			.debug_frame	300248	300248	0	0.0
			.debug_info	20275630	20275631	1	0.0
			.debug_line	2660982	2660982	0	0.0
			.debug_loc	2804957	2804957	0	0.0
			.debug_ranges	283168	283168	0	0.0
			.debug_str	3026158	3026158	0	0.0
			.ramVecs	780	780	0	0.0
			.resetVecs	64	64	0	0.0
			.rodata	105993	105993	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	379204	379204	0	0.0
			.symtab	256912	256912	0	0.0
			.text	536984	536984	0	0.0