[Floaty] Don't emit cancel event when effect is disabled

Bug: 426144919
Test: SqueezeEffectInteractorTest
Test: Manual, i.e. verified that cancel events are only emitted when
      the effect is enabled
Flag: com.android.systemui.shared.enable_lpp_assist_invocation_effect
Change-Id: I7cfbaf93f62508f629700b7601ab028329d290e7