Do not enforce websocket restriction on proxy

[acormier-maia]

Remove the restriction that the leaf node connection must be a websocket in order to enable proxy support. I have tested locally and confirms it works.

leafnodes {
  remotes [{
    urls: [nats-leaf://remote-server.example.com"]
    
    proxy {
      url: "http://corporate-proxy.company.com:8080"
      username: "proxy_user"
      password: "proxy_pass"
      timeout: "30s"
    }
  }]
}

Signed-off-by: Austin Cormier austincormier@maiaedge.io