[flexiglass] Remove SceneLogger#logSceneChangeCommitted.

The historical reason for the distinction between scene change
"requested" vs "committed" was that there was a disconnect between where
you request the scene change and where that scene change actually
happens. This is no longer true now that the data source is STL itself.

Bug: 359173565
Flag: com.android.systemui.scene_container
Test: Updated affected unit tests.
Change-Id: I94a3beb99c3a557cbc4057c0874f3a8139402faf