Fix doc comment

Mistake when merging

wpiutil/src/main/java/edu/wpi/first/util/struct/Struct.java

@@ -145,7 +145,7 @@ static void packArray(ByteBuffer bb, double[] arr) {
     }
   }
 
-  /*
+  /**
    * Returns whether or not objects are immutable. Immutable objects must also be comparable using
    * the equals() method. Default implementation returns false.
    *