Increase the upper limit of slang target API to 31. am: 5ad64063ee am: f5ca73da36 am: 8136a922d0

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/compile/slang/+/14470202

Change-Id: Id97296b68cd10635748fc737e6ba5dbfd07d5a85