Cleanup: use shared apex_key am: a0b0a624ff

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2780407

Change-Id: Iad2389a8d276503afec02eb27ded4a994a9217be
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>