Removing all dependencies of launcher code on wallpaper-picker

> WallpaperPicker can still depend on launcher code, but not the
other way round.

Change-Id: I93a07f985c3955c638a68a5fad9c09b184a879b9
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index fb7ac3f..82ee8f2 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -128,7 +128,7 @@
         </activity>
 
         <activity
-            android:name="com.android.launcher3.LauncherWallpaperPickerActivity"
+            android:name="com.android.launcher3.WallpaperPickerActivity"
             android:theme="@style/Theme.WallpaperPicker"
             android:label="@string/pick_wallpaper"
             android:icon="@mipmap/ic_launcher_wallpaper"