Clean up fully rolled out PermissionMigrationForZeroTrustImplEnabled Flag was rolled out in Android V. Bug: 364998990 Test: TH Flag: EXEMPT flag cleanup (cherry picked from https://googleplex-android-review.googlesource.com/q/commit:dfdf7fb5acd44bcccb2d119793727683fe1654a7) Merged-In: I25f472268b075d79cc0a0378a55b515694109cbe Change-Id: I25f472268b075d79cc0a0378a55b515694109cbe