Make apexer replace instances of version placeholder strings with the am: ff9a15cde1 am: c35a20263f

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/apex/+/17949768

Change-Id: Ic1aae117eb98088e0948d7bc2028af21e2cfe074
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>