Relax the assertion for MapsEnterPipTest for UI mode change

Going from fullscreen Maps to PiP goes through UI mode change that adds
a snapshot overlay during the transition. Relax the assertion to test
only the start/end state.

Bug: 314838452
Test: atest MapsEnterPipTest
Change-Id: I8e3175c80d65770c5b44f9617221c843b7ec9679
1 file changed