Update README.md

Author: ggilmore

README.md

@@ -28,6 +28,7 @@ Run `yarn` so that you install all the necessary dependencies.
 - `yarn up`: creates a new GKE cluster and fetches the necessary credentials
 - `yarn destroy`: deletes a GKE cluster that was previously created with `yarn up`
 - `yarn auth`: fetch the credentials so that kubectl can speak to the cluster
+- `yarn deauth`: remove the cluster's kubectl credentials
 - `yarn web`: opens the GCP page for your cluster in your webrowser
 
 ## Troubleshooting