Remove the keep clear areas XML tag from Hotseat

It reports its size through SystemUiProxy and this tag causes it to
report the region twice. Additionally upon screen rotation the value
is getting updated with a delay, so for a moment two keep clear areas
for Launcher are present - one from the previous orientation (on the
side), and one from the current orientation (matching the proxy value
in unrestrictedKeepClearAreas).

Bug: 285242520
Test: before http://recall/-/ekEuGtt9d9HWqkUtAzpHx8/cLtiXGYUyItm2kNCCEkkWA
Test: after http://recall/-/ekEuGtt9d9HWqkUtAzpHx8/iPs6fwdSXG3TE0IERmxA8
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:b5b218eea929f719703ca91df6b9868645909f4c)
Merged-In: I40dfe08680c944f2be5db0f6b15515492f409565
Change-Id: I40dfe08680c944f2be5db0f6b15515492f409565