Revert^3 "Add the mainline framework boot image extension to the default." am: 03a88039ce

Original change: https://android-review.googlesource.com/c/platform/art/+/2465993

Change-Id: I8eddbf14f711aea180da11a494e48a3c56a97ac8
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>