Fixes no dim surface boost when starting home

The TaskFragment#mVisibleRequested is false when home
started and therefore the dim surface was not boost
during the transition animation.

Drops the #isVisibleRequested check since the visibility
of the activity window is still checked in #shouldBoostDimmer.

Bug: 323080222
Test: repro steps on the bug
Change-Id: Ia0242ccf6026da4061acdc752fad35bc36a25b16