Remove Android.mk from bump.py

The file no longer exists and everything is handled in the Android.bp
file instead. The script was previously modified to handle the
Android.bp file.

Test: build/make/tools/finalization/build-step-0-and-m.sh cf_x86_64_phone
Bug: 331696132
Change-Id: I08bd6d40fd4b003d9c5f927e06288922c5e16202