Remove unused Android.mk am: 1f8ef931c8

Original change: https://android-review.googlesource.com/c/platform/tools/test/graphicsbenchmark/+/2826052

Change-Id: I7e4a1fc624c335fe43cfee145b506d60b216d430
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>