Update ActivityTransitionTests for shell transit

When shell transitions are enabled we don't dump a value for lastUsedAppTransition in the proto trace so getWmState().getDefaultDisplayLastTransition() always returns TRANSIT_NONE for 0.

Just checking the app transition state should be robust enough.

Test: atest CtsWindowManagerDeviceTestCases:ActivityTransitionTests with shell transitions enabled

Bug: 233597493
Change-Id: I2330f244c6cdc95c37627bfb8acb6ef3c1aa59e1