[flexiglass] Avoid extra recomposition in pattern bouncer.

By removing the recomposition, we get better performance but also might
be able to get a less flaky BouncerSceneScreenshotTest.

Bug: 310704139
Test: manually verified that the pattern bouncer still behaves properly
Flag: ACONFIG com.android.systemui.scene_container DEVELOPMENT
Change-Id: Iac17977714f2e8a86c7d7468348469a4b6779f7c