google_pixel: ThemePickerGoogle: Properly override the activity

* Prevents duplicated "Styles" apps of which Android
  will prompt the user which to use.

Change-Id: I178d03a918c28975b56f6719f9601ea26c651611

ThemePickerGoogle/AndroidManifest.xml

@@ -32,8 +32,7 @@
             android:label="@string/app_name"
             android:exported="true">
             <intent-filter>
-                 <action android:name="android.intent.action.SET_WALLPAPER"/>
+                  <action android:name="android.intent.action.MAIN"/>
-                 <category android:name="android.intent.category.DEFAULT"/>
             </intent-filter>
         </activity-alias>