robot-name: add hint to @Ignore annotations

exercises/robot-name/src/test/java/RobotTest.java

@@ -22,13 +22,13 @@ public class RobotTest {
         assertIsValidName(robot.getName());
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void differentRobotsHaveDifferentNames() {
         assertThat(robot.getName(), not(equalTo(new Robot().getName())));
     }
 
-    @Ignore
+    @Ignore("Remove to run test")
     @Test
     public void resetName() {
         final String name = robot.getName();