Remove testCloseTask_BothWallpaper_SlowStop FlakyTest tag. Since CL If1907d71135158bafea69881205f351ab666025e has already fixed test flakiness, remove FlakyTest tag to let the test as presubmit. Fix: 139111132 Test: atest TransitionSelectionTests#testCloseTask_BothWallpaper_SlowStop Change-Id: Ic53e0228bd6d23cb3fff54bbda0f9d048dbd9198