Remove unused Android.mk am: 1f8ef931c8

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

Change-Id: I2e665c110172430c4aca8d33e025b97d8f8e3287
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>