website/docs: use common placeholders for forward_auth

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

website/docs/providers/proxy/_nginx_proxy_manager.md

@@ -32,7 +32,7 @@ location / {
 
 # all requests to /akprox must be accessible without authentication
 location /akprox {
-    proxy_pass          http://*ip or hostname of the authentik OUTPOST*:9000/akprox;
+    proxy_pass          http://outpost.company:9000/akprox;
     # ensure the host of this vserver matches your external URL you've configured
     # in authentik
     proxy_set_header    Host $host;