Make notification icon less similar to superuser icon.

briar-android/src/main/res/drawable/ongoing_notification_icon.xml

+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24dp"
+        android:height="24dp"
+        android:viewportHeight="329.40625"
+        android:viewportWidth="329.40625">
+	<path
+		android:fillColor="#ffffff"
+		android:pathData="M164.7,0C73.7,0 0,73.7 0,164.7c0,91 73.7,164.7 164.7,164.7 91,0 164.7,-73.8 164.7,-164.7 0,-91 -73.8,-164.7 -164.7,-164.7zM111.7,46.6 L120,46.6c9.7,0 17.7,8 17.7,17.7l0,22.5 -43.7,0 0,-22.5c0,-9.7 8,-17.7 17.7,-17.7zM208.7,46.6 L217,46.6c9.8,0 17.7,8 17.7,17.7l0,119.5 -43.7,0 0,-119.5c0,-9.7 8,-17.7 17.7,-17.7zM64.5,93.8l119.5,0 0,43.7 -119.5,0c-9.8,0 -17.7,-8 -17.7,-17.7l0,-8.3c0,-9.8 8,-17.7 17.7,-17.7zM241.7,93.8 L264.2,93.8c9.7,0 17.6,8 17.7,17.7l0,8.3c0,9.8 -8,17.7 -17.7,17.7l-22.5,0 0,-43.7zM94,144.5l43.7,0 0,119.5c0,9.7 -8,17.7 -17.7,17.7l-8.3,0c-9.8,0 -17.7,-8 -17.7,-17.7l0,-119.5zM64.5,190.8 L87,190.8 87,234.5 64.5,234.5c-9.8,0 -17.7,-8 -17.7,-17.7l0,-8.3c0,-9.8 8,-17.7 17.7,-17.7zM144.7,190.8 L264.2,190.8c9.7,0 17.6,8 17.7,17.7l0,8.3c0,9.7 -8,17.7 -17.7,17.7l-119.5,0 0,-43.7zM191,241.5 L234.7,241.5 234.7,264c0,9.7 -8,17.7 -17.7,17.7l-8.3,0c-9.7,0 -17.7,-8 -17.7,-17.7l0,-22.5z"/>
+</vector>