Be more specific about template type for GoalCallback

Signed-off-by: Jacob Perron <jacob@openrobotics.org>

Author: jacobperron

rcljava/src/main/java/org/ros2/rcljava/action/GoalCallback.java

@@ -15,9 +15,9 @@
 
 package org.ros2.rcljava.action;
 
-import org.ros2.rcljava.interfaces.MessageDefinition;
+import org.ros2.rcljava.interfaces.GoalRequestDefinition;
 
-public interface GoalCallback<T extends MessageDefinition> {
+public interface GoalCallback<T extends GoalRequestDefinition> {
   public enum GoalResponse {
     REJECT,
     ACCEPT,