[Floaty] Remove obsolete TopLevelWindowEffectsThread

Bug: 411435519
Flag: com.android.systemui.shared.enable_lpp_assist_invocation_effect
Test: TopLevelWindowEffectsTest
Test: Manual, verified that effect works as expected
Change-Id: Iaf0617e3c9040e8ae2a546bbf0adbd7771ecac5c