Revert "certify_bootimg: support --extra_footer_args"

This reverts commit f754a7c3b8fcff3f74ad67a7c8138d97c3d9e879.

After more thoughts, decided to use another approach: retaining
the AVB properties from the original footer. So no need to use
--extra_footer_args to add new AVB properties.

With this approach, the certify_bootimg script can focus on
boot signature generation without involving too much in the
AVB footer generation.

Bug: 232062499
Test: atest --host certify_bootimg_test
Change-Id: Ie11c2a144cf3a1f33b25fc2ad25ffe2c80b73518
2 files changed