Use APPLY text button for grid picker am: 82c09c5e89 am: 3a7b68037c

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/ThemePicker/+/14957119

Change-Id: I5e3cffbd7ec972d3b31cff7e7c5e6a1f3e448013