Change token example to add node only (#11004)
Change token example to add node only (#11004)

* Change token example to add node only

Given that it's not possible to join a proxy server via proxy address (`teleport.example.com:443`) and there relatively few circumstances where people would want to add both `node` and `proxy` services on one cluster, I think this example is likely to cause more confusion than anything else.

* Update adding-nodes.mdx

Remove static token example and tidy up
gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport,gravitational/teleport