Remove unused method

Summary: Removes `BundleDownloader#cancelDownloadBundleFromURL`

Reviewed By: pakoito

Differential Revision: D6900903

fbshipit-source-id: d9297344d6296d79a984aeecb3e014c9ed23a165

Author: davidaurelio

ReactAndroid/src/main/java/com/facebook/react/devsupport/BundleDownloader.java

@@ -198,13 +198,6 @@ public void execute(Map<String, String> headers, Buffer body, boolean finished)
     });
   }
 
-  public void cancelDownloadBundleFromURL() {
-    if (mDownloadBundleFromURLCall != null) {
-      mDownloadBundleFromURLCall.cancel();
-      mDownloadBundleFromURLCall = null;
-    }
-  }
-
   private void processBundleResult(
       String url,
       int statusCode,