Remove unlaunched ENABLE_UNFOLD_STATUS_BAR_ANIMATIONS flag

This flag was introduced to test enabling/disabling an unfold animation,
but isn't launched and isn't relevant anymore.

Bug: 265764985
Flag: EXEMPT refactor
Test: verify status bar still works on fold & unfold
Test: atest PhoneStatusBarViewControllerTest
Change-Id: Id158be7014ccb237b69d4384a2767323c9b7ba14