[HUDI-726]Delete unused method in HoodieDeltaStreamer (#1426)

hudi-utilities/src/main/java/org/apache/hudi/utilities/deltastreamer/HoodieDeltaStreamer.java

@@ -576,8 +576,4 @@ public class HoodieDeltaStreamer implements Serializable {
       }, executor)).toArray(CompletableFuture[]::new)), executor);
     }
   }
-
-  public DeltaSyncService getDeltaSyncService() {
-    return deltaSyncService;
-  }
 }