Polishing.

Make sure type used in protected method is visible in defined scope.

See: #4846

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

@@ -3261,7 +3261,7 @@ public class MongoTemplate
 	 * @author Thomas Darimont
 	 */
 
-	interface DocumentCallback<T> {
+	protected interface DocumentCallback<T> {
 
 		T doWith(Document object);
 	}