docs: update contributing path in README (#147)

Author: callmehiphop

core/packages/nodejs-proto-files/README.md

@@ -75,7 +75,7 @@ More Information: [Google Cloud Platform Launch Stages][launch_stages]
 
 ## Contributing
 
-Contributions welcome! See the [Contributing Guide](https://github.com/googleapis/nodejs-proto-files/blob/master/.github/CONTRIBUTING.md).
+Contributions welcome! See the [Contributing Guide](https://github.com/googleapis/nodejs-proto-files/blob/master/CONTRIBUTING.md).
 
 ## License