Remove unnecessary UnsupportedAppUsage annotation

These annotations were part of the initial bulk assignment of
annotations, but do not have any active usage. Further, the
start() method is not annotated so there is no clear way for
applications to trigger any meaningful behavior.

Bug: 149293249
Test: built and surveyed for potential API usage
Change-Id: I4118d6d54562079c3c4e4a83fd0e40b50cb08434