Clean up the flag create_windowless_window_magnifier

Bug: 377211958
Bug: 286466144
Test: atest SystemUITests:WindowMagnificationControllerTest
Test: atest SystemUITests:WindowMagnificationAnimationControllerTest
Flag: com.android.systemui.create_windowless_window_magnifier
Change-Id: I2a6021a740f54d27a3e657b572ef93ad1a09a542
5 files changed