Adjust the space at the top/bottom of the category and wallpaper pages. am: 76a5f8df62 am: 97e5d4e120

Original change: https://googleplex-android-review.googlesource.com/c/platform/packages/apps/WallpaperPicker2/+/11675390

Change-Id: I3109a13c5ede44cf535cdf217d62dcf7e1ce389c