Remove creating mutable states for the animation

With the new sliders an old logic of enabled-disabled state transition
without an animation is no longer relevant so we can omit that altogether.

Flag: com.android.systemui.volume_redesign
Fixes: 405549844
Test: atest VolumeDialogScreenshotTest
Test: manual on foldable. Adjust volume with swipes and physical buttons
and observe the animation

Change-Id: Iaf2caf079b160be356d3a117430a635b09e789e5