Fix the copyright sample for CONTRIBUTING

Author: drakeet

CONTRIBUTING.md

@@ -13,7 +13,7 @@ All files are released with the Apache 2.0 license.
 If you are adding a new file it should have a header like this:
 
 ```
-/**
+/*
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at