Revert "Snap to last task if swiping down at a greater Y than X velocity."

This reverts commit e10ab8cd.

Reason for revert: Possibly introduced regressions. There was a followup to this CL that was also reverted. Would prefer to revert this one too and then roll forward with a CL that addresses all problems.

Change-Id: Ic32ad10945e4ace2f985475d24adb6a80b19067f