Revert "[avb_footer] Add avb_gen_vbmeta_image to generate vbmeta..."

Revert submission 2375848-initrd_avb_footer

Reason for revert: build break

Reverted changes: /q/submissionid:2375848-initrd_avb_footer

Bug: 264940248
Change-Id: Iab44c187183a5d8eeefc952910e6262fc63627de