remove android:exported attribute from unstable xml

app/src/unstable/AndroidManifest.xml

@@ -7,8 +7,7 @@
     <application>
         <receiver android:name=".receivers.InstallReceiver" />
 
-        <activity android:name=".activities.MainActivity"
-            android:exported="true">
+        <activity android:name=".activities.MainActivity">
             <intent-filter android:autoVerify="true">
                 <action android:name="android.intent.action.VIEW" />
                 <action android:name="android.media.action.MEDIA_PLAY_FROM_SEARCH" />