clarify port requirements for reverse proxy when using with old multi-container setup (#652)

Author: shuuri-labs

src/pages/selfhosted/migration/enable-reverse-proxy.mdx

@@ -159,7 +159,7 @@ NB_PROXY_CERTIFICATE_DIRECTORY=/certs
 ```bash
 NB_PROXY_DOMAIN=proxy.example.com
 NB_PROXY_TOKEN=nbx_your_token_here
-NB_PROXY_MANAGEMENT_ADDRESS=http://management:443
+NB_PROXY_MANAGEMENT_ADDRESS=http://management:33073
 NB_PROXY_ALLOW_INSECURE=true
 NB_PROXY_ADDRESS=:8443
 NB_PROXY_ACME_CERTIFICATES=true