Delete BUILD file now that can auto-generate it with bp2build. am: d5ad8a1c79

Original change: https://android-review.googlesource.com/c/platform/packages/apps/WallpaperPicker/+/2547730

Change-Id: If82f8c1c33451055279e8838fd8e76fcac15da64
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>