Unregister listeners from ClockRegistry when destroyed am: e980bd3a5d

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

Change-Id: I150a03b8e6fbab275e92e359869df5cefa9e107a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>