Remove unsupportedappusage_index.csv from droidcore target.

out/soong/hiddenapi/hiddenapi-index.csv produced by a singleton rule replaced the target.

Test: m
Bug: 145132366
Change-Id: I29267c179f301ebcb128d615229858ced549d670
Merged-In: I29267c179f301ebcb128d615229858ced549d670