CentralSurfacesImpl#onStatusBarWindowStateChanged check for correct flag

Before, this refactor was behind status_bar_simple_fragment, but now it
is behind status_bar_connected_displays.

Test: CentralSurfacesImplTest
Bug: 362720336
Flag: com.android.systemui.status_bar_connected_displays
Change-Id: Ibcbb543de14666cbad86b27c99a5cca1090a8d1a