docs: add warning not to enable Consul tls.grpc.verify_incoming (#19970)

Consul does not support incoming TLS verification of Envoy. This failure results
in hard-to-understand errors like `SSLV3_ALERT_BAD_CERTIFICATE` in the Envoy
allocation logs. Leave a warning about this to users.

Closes: https://github.com/hashicorp/nomad/issues/19772
Closes: https://github.com/hashicorp/nomad/issues/16854
Ref: https://github.com/hashicorp/consul/issues/13088

website/content/docs/configuration/consul.mdx

@@ -156,6 +156,16 @@ agents with [`client.enabled`][] set to `true`.
   certificate used for communication between Connect sidecar proxies and Consul
   agents. Will default to the `CONSUL_GRPC_CACERT` environment variable if set.
 
+  <Warning>
+  
+    Consul does not support incoming TLS verification of Envoy
+    sidecars. You should set `tls.grpc.verify_incoming = false` in your
+    Consul configuration when using Connect. See 
+    [Consul/#13088](https://github.com/hashicorp/consul/issues/13088) for
+    more details.
+    
+  </Warning>
+
 - `share_ssl` `(bool: true)` - Specifies whether the Nomad client should share
   its Consul SSL configuration with Connect Native applications. Includes values
   of `ca_file`, `cert_file`, `key_file`, `ssl`, and `verify_ssl`. Does not