DATAMONGO-2618 - Fix visibility of ReplaceRootDocumentOperation.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/aggregation/ReplaceRootOperation.java

@@ -155,7 +155,7 @@ public class ReplaceRootOperation implements FieldsExposingAggregationOperation
 	 *
 	 * @author Mark Paluch
 	 */
-	static class ReplaceRootDocumentOperation extends ReplaceRootOperation {
+	public static class ReplaceRootDocumentOperation extends ReplaceRootOperation {
 
 		private final static ReplacementDocument EMPTY = new ReplacementDocument();
 		private final ReplacementDocument current;