fix typo

contrib/terraform/openstack/README.md

@@ -421,7 +421,7 @@ kubectl version
 
 If you are using floating ip addresses then you may get this error:
 ```
-Unable to connect to the server: x509: certificate is valid for 10.0.0.6, 10.0.0.6, 10.233.0.1, 127.0.0.1, not 132.249.238.25
+Unable to connect to the server: x509: certificate is valid for 10.0.0.6, 10.233.0.1, 127.0.0.1, not 132.249.238.25
 ```
 
 You can tell kubectl to ignore this condition by adding the