Client agent docs updates (#5180)

* docs/client-agent: indent PAN docs correctly

Identifying the primary network interface is a sub-heading under the
PAN troubleshooting section.

* docs/transparent-sessions: add known issue around containers/VMs

VMs/containers that do not have access to the local network cannot
use aliases through transparent sessions.

website/content/docs/api-clients/client-agent.mdx

@@ -532,7 +532,7 @@ override_upstream_dns_servers = [
 ]
 ```
 
-### Primary network interfaces
+#### Primary network interfaces
 
 By default, the Client Agent creates IPs on the primary network interface to serve its DNS server.
 Refer to the tabs below for possible conflicts for each supported operating system.