Unregister listeners from ClockRegistry when destroyed am: e980bd3a5d

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/ThemePicker/+/23407197

Change-Id: I059597d0ee59d69d8d270a5af15d34363f04e791
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>