Unregister listeners from ClockRegistry when destroyed am: e980bd3a5d am: 29920aef25 am: ac279e1cf7 am: 1eb5d40031

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

Change-Id: I77981936adc6ca27acf6b3a62a8245b957124541
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>