WidgetCell & LiveWidgetPreview cleanup am: ae6b34811b

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Launcher3/+/13790508

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I7bf6e7470f2a96f5b93d56b35c3cebc41954cea2