Add content description to screensaver customization button am: ca65b6e5 am: 2c7a55ed

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/Settings/+/21268649



Change-Id: I12f0b44070c9b28bf99d1fd442bb6f831c414db1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>