Revert "Deprecate .fsv_sig"

Revert submission 24590927-deprecate_fsv_sig

Reason for revert: b/299494922

Reverted changes: /q/submissionid:24590927-deprecate_fsv_sig

Change-Id: I1ecc3ea2a1387b92e98ebdea225476989d08b599
2 files changed