Remove unused WallpaperConnectionListener.

It also fix LinearLayout in ThemeFragment leaked at WallpaperConnection.mListener.

Bug: 158093441
Change-Id: I1127467edc535e5c2e7f257bd3f5a40551eec27b
diff --git a/src/com/android/customization/picker/WallpaperPreviewer.java b/src/com/android/customization/picker/WallpaperPreviewer.java
index 8f69d59..c8b4bf2 100644
--- a/src/com/android/customization/picker/WallpaperPreviewer.java
+++ b/src/com/android/customization/picker/WallpaperPreviewer.java
@@ -164,10 +164,7 @@
 
         mWallpaperConnection = new WallpaperConnection(
                 getWallpaperIntent(homeWallpaper.getWallpaperComponent()), mActivity,
-                new WallpaperConnection.WallpaperConnectionListener() {
-                    @Override
-                    public void onEngineShown() {}
-                }, mPreviewGlobalRect);
+                /* listener= */ null, mPreviewGlobalRect);
 
         LiveTileOverlay.INSTANCE.update(new RectF(mPreviewLocalRect),
                 ((CardView) mHomePreview.getParent()).getRadius());