docs: switch to signed images #511

Job	Run time
Build akmods package (37, 470)	8m 35s
Build akmods package (37, 535)	8m 51s
Build akmods package (38, 530)	6m 27s
Build akmods package (38, 535)	6m 29s
Build and push image (silverblue, 37, 470)	1m 47s
Build and push image (silverblue, 37, 535)	1m 38s
Build and push image (silverblue, 38, 530)	1m 48s
Build and push image (silverblue, 38, 535)	2m 5s
Build and push image (kinoite, 37, 470)	2m 11s
Build and push image (kinoite, 37, 535)	2m 16s
Build and push image (kinoite, 38, 530)	2m 13s
Build and push image (kinoite, 38, 535)	2m 8s
Build and push image (vauxite, 37, 470)	2m 23s
Build and push image (vauxite, 37, 535)	2m 6s
Build and push image (vauxite, 38, 530)	2m 23s
Build and push image (vauxite, 38, 535)	2m 1s
Build and push image (sericea, 38, 530)	1m 52s
Build and push image (sericea, 38, 535)	1m 46s
Build and push image (base, 37, 470)	1m 25s
Build and push image (base, 37, 535)	1m 28s
Build and push image (base, 38, 530)	1m 29s
Build and push image (base, 38, 535)	1m 57s
Build and push image (lxqt, 37, 470)	2m 0s
Build and push image (lxqt, 37, 535)	1m 59s
Build and push image (lxqt, 38, 530)	2m 8s
Build and push image (lxqt, 38, 535)	1m 40s
Build and push image (mate, 37, 470)	2m 16s
Build and push image (mate, 37, 535)	1m 56s
Build and push image (mate, 38, 530)	2m 17s
Build and push image (mate, 38, 535)	2m 4s
	1h 21m 38s

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