Fix navigation path in authentication configuration docs (#5508)

`"Authentication"` was renamed to `"Access Control Backends"` in the UI.

Author: jrauh01

doc/05-Authentication.md

@@ -8,7 +8,7 @@ or if users are spread over multiple places.
 
 ## Configuration <a id="authentication-configuration"></a>
 
-Navigate into **Configuration > Application > Authentication **.
+Navigate into **Configuration > Application > Access Control Backends**.
 
 Authentication methods are configured in the `/etc/icingaweb2/authentication.ini` file.