Promote ImeInsetsSourceConsumerTest from FlakyTest

This has been marked conservatively as FlakyTest since 2019
but no bugs have ever been filed about its flakiness. Promote
it so it can be part of presubmit runs.

Change-Id: Icf69d254a493e9a02669ac6f3b3875942bd036cf
Test: atest --iterations 200 ImeInsetsSourceConsumerTest
Bug: 118118435