unset Proxy header in proxy config

manifests/config.pp

@@ -92,6 +92,7 @@ class nginx::config(
     'Host $host',
     'X-Real-IP $remote_addr',
     'X-Forwarded-For $proxy_add_x_forwarded_for',
+    'Proxy ""',
   ],
   $proxy_hide_header              = [],
   $sendfile                       = 'on',