Revert "Add the mainline framework boot image extension to the default." am: 51754b8608 am: abbc7f763b am: 24fefa1e0c

Original change: https://android-review.googlesource.com/c/platform/art/+/2458429

Change-Id: Id029ae0382a6ab4f702769d4fae273bcc4a7809a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>