Remove unused AllocationBacking am: 8941e34d37 am: 1675211aa9 am: e4e0ffdf0f

Original change: https://android-review.googlesource.com/c/platform/frameworks/base/+/2722393

Change-Id: I6d05e609005d1941b866ea090544ea279074bd99
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>