Move setLayerStack back to max-sdk-o greylist.

The API was dark grey listed in P, and it was greylisted in commit
76907eea.

Move it back as we should not be making API less restrictive in new
letter releases.

Test: m
Bug: 123987101
Change-Id: I0b43e31cb1d3d1c170d6718d3f71e21841ec30dc