docs: update contributing path in README (#275)

Author: callmehiphop

packages/google-cloud-dialogflow/README.md

@@ -126,7 +126,7 @@ More Information: [Google Cloud Platform Launch Stages][launch_stages]
 
 ## Contributing
 
-Contributions welcome! See the [Contributing Guide](https://github.com/googleapis/nodejs-dialogflow/blob/master/.github/CONTRIBUTING.md).
+Contributions welcome! See the [Contributing Guide](https://github.com/googleapis/nodejs-dialogflow/blob/master/CONTRIBUTING.md).
 
 ## License