Cleanup listener reference in Screen Attention

This will fix a memory leak being caused by dangling listeners.

Test: locally with oriole, make RunSettingsRoboTests -j$(nproc) ROBOTEST_FILTER=AdaptiveSleepCameraStatePreferenceControllerTest,AdaptiveSleepPreferenceControllerTest

Bug: 245990072
Change-Id: I35eeedc3ece719f1f3baff6235cc5ac2d42fbba3