Documentation: change `etcdctl role remove` to `etcdctl role delete`
This is a document error. With running `etcdctl role --help`, we can find that it should be delete, not remove.
Fixes
@@ -119,7 +119,7 @@ $ etcdctl role revoke-permission myrolename /foo/bar
As is removing a role entirely:
```
-$ etcdctl role remove myrolename
+$ etcdctl role delete myrolename
```
## Enabling authentication
