Remove extraneous transition from Overview to Home screen

Previously, users used to be able to swipe down near the
bottom of the screen to leave overview. This was causing the taskbar to
animate to home while still in overview (and causing jank). Since this isn't expected behavior for
how to leave overview, this change removes that method.

Flag: N/A
Fix: 284416178
Test: Completed multiple transitions (ex. Overview to home) with 3
button nav and gesture nav. Ensured swiping down from below the recents
task does not go to the home screen while not affecting other
transitions.

Change-Id: I8cdfde71117dd947174d9c3c3a7f834fbeaddcca