Revert "signer: Check the list of android image files"

This reverts commit 48532e571bf79f32af972f6096681c11674c3825.

Reason for revert: Stable roll blocked due to unit test failures in platform/signing.
https://ci.chromium.org/ui/p/chromeos/builders/cq/fullcheckout-presubmit/b8813887760837459473/overview

Original change's description:
> signer: Check the list of android image files
>
> BUG=b:230434967
> BRANCH=None
> TEST=Run ./sign_official_build.sh locally
>
> Signed-off-by: Daichi Hirono <hirono@chromium.org>
>
> Change-Id: I5e8b4d848f30f53fae58c721c9b7ddcfbfea9852
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/3607891
> Tested-by: Daichi Hirono <hirono@chromium.org>
> Commit-Queue: Daichi Hirono <hirono@chromium.org>
> Reviewed-by: Shao-Chuan Lee <shaochuan@chromium.org>

Bug: b:230434967
Change-Id: I185562d6dcbac4fd30b6dc4c331bd0b1508d58e8
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/3644484
Commit-Queue: Daichi Hirono <hirono@chromium.org>
Tested-by: Daichi Hirono <hirono@chromium.org>
Reviewed-by: Shao-Chuan Lee <shaochuan@chromium.org>
Auto-Submit: Daichi Hirono <hirono@chromium.org>