Centers affordance options when wide. am: 7d68d03954 am: 4278d32c83

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/ThemePicker/+/21272336

Change-Id: I91c4a0bbc7b95f22886aafbd1aae81254efa4d2e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>