Use appropriate start padding for clear all button

This still shows up a bit strange with
notched phones because we are using
RecentsView padding to give ClearAll the
right amount of spacing. However, we're only
adding padding to the left and right and not
the top/bottom.
That's captured here: b/154436527

Fixes: 150389833
Test: Tested landscape/portrait/seascape
launcher, w/ RTL as well

Change-Id: I49defd58048e609a1f7a821abb97374bcbb94b9f