Move setTarget() to max-sdk-o greylist.

This method was on the dark grey list in P. It was removed sometime in
the meantime, and re-added in commit 01053cd7, but put onto the grey list
rather then the max-sdk-o greylist (equivalent to dark grey in P).

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

Test: m
Bug: 123987101
Change-Id: I5ec57e6523f2d0881e0e4e5597009fc2717bfb85