fix scala style

Author: WeichenXu123

mllib/src/main/scala/org/apache/spark/ml/source/image/ImageDataSource.scala

@@ -48,4 +48,4 @@ package org.apache.spark.ml.source.image
  * @note This class is public for documentation purpose. Please don't use this class directly.
  * Rather, use the data source API as illustrated above.
  */
-class ImageDataSource private() {}
+class ImageDataSource private() {}