Android U Beta 4 GPL
Set sdk_version for error_prone_core am: 91a4314704 am: 7647128ca3

Original change: https://android-review.googlesource.com/c/platform/external/error_prone/+/2521118

Change-Id: Ia0ffa648d241c19c7a1e9dddd340b83f8762ffea
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>