Messaging: Remove low storage handling

* SMS are the least of your storage issues, if you reach the limit
* Both Intent.ACTION_DEVICE_STORAGE_LOW and
  Intent.ACTION_DEVICE_STORAGE_LOW are not delivered to apps after O
* Remove all now unused strings from all languages - we don't sync those
  with crowdin (yet)

Change-Id: If01f937acdafbb34d5a9e792db54de4761ec4cc5

src/com/android/messaging/ui/UIIntents.java

@@ -319,11 +319,6 @@ public abstract class UIIntents {
             final int updateTargets, final ConversationIdSet conversationIdSet,
             final int requestCode);
 
-    /**
-     * Get a PendingIntent for showing low storage notifications.
-     */
-    public abstract PendingIntent getPendingIntentForLowStorageNotifications(final Context context);
-
     /**
      * Get a PendingIntent for showing a new message to a secondary user.
      */