website/docs: Corrected typo and added Note about port number if using Istio/Kubern… (#4851)

* Corrected typo and added Note about port number if using Istio/Kubernetes

@BeryJu I was reading [this article](https://prevue.ch/news/2022-10-11-istio-authentik/) about a fellow setting up authentik, using Istio and Kubernetes. I wanted to somehow add a heads up about the port number, but I am not confident that I got it right. Is it only if there are custom decisions being made that the port number has to be for the cluster? 

Signed-off-by: Tana M Berry <tanamarieberry@yahoo.com>

* Update website/docs/providers/proxy/forward_auth.mdx

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

* fix lint error

Signed-off-by: Jens Langhammer <jens@goauthentik.io>

---------

Signed-off-by: Tana M Berry <tanamarieberry@yahoo.com>
Signed-off-by: Jens L. <jens@beryju.org>
Signed-off-by: Jens Langhammer <jens@goauthentik.io>
Co-authored-by: Jens L <jens.langhammer@beryju.org>
Co-authored-by: Jens Langhammer <jens@goauthentik.io>

website/docs/providers/proxy/forward_auth.mdx

@@ -107,7 +107,7 @@ import TraefikIngress from "./_traefik_ingress.md";
   </TabItem>
 </Tabs>
 
-## Enovy (Istio)
+## Envoy (Istio)
 
 :::info
 Requires authentik 2022.6
@@ -117,6 +117,10 @@ Requires authentik 2022.6
 Support for this is still in preview, please report bugs on [GitHub](https://github.com/goauthentik/authentik/issues).
 :::
 
+:::info
+If you are using Istio and Kubernetes, use the port number that is exposed for your cluster.
+:::
+
 <Tabs
   defaultValue="envoy-istio"
   values={[