Revert^2 "Add the mainline framework boot image extension to the default." am: 43f9a4abb8 am: ca4164de75

Original change: https://android-review.googlesource.com/c/platform/art/+/2458432

Change-Id: Ia7f75a1359b4407e3e789e7ee1e19658bc8e2562
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>