docs: updated nginx tunning section with modification allowing custom https port to work.

- fixes  #5408

docs/admin/nginx-tuning.rst

@@ -9,7 +9,7 b' timeout during large pushes.'
 .. code-block:: nginx
 
     proxy_redirect              off;
-    proxy_set_header            Host $host;
+    proxy_set_header            Host $http_host;
 
     ## needed for container auth
     # proxy_set_header            REMOTE_USER $remote_user;