Remove assumptions about specific transition types for identifying recents

- There is not particular guarantee that transitions will be started
  with a specific type, in this case, we already set
  TRANSIT_FLAG_IS_RECENTS when starting a transient transition to
  home, so we can just check that directly

Fixes: 398161346
Flag: com.android.wm.shell.enable_recents_bookend_transition
Test: atest FullScreenMagnificationGestureHandlerTest
Change-Id: I35cc0b15598385896321d570e14983be9a0cf4a0