Improve provisioner docs (nginx#741)

Problem:
It is not obvious that it is necessary to re-build the NKG image to
customize the static mode Deployment, which the provisioner uses.

Solution:
Make the docs clearer.

---------
Co-authored-by: Saylor Berman <s.berman@f5.com>
Co-authored-by: Kate Osborn <50597707+kate-osborn@users.noreply.github.com>

Author: 3 people

conformance/provisioner/provisioner.md

@@ -15,10 +15,14 @@ Global Flags:
       --gatewayclass string        The name of the GatewayClass resource. Every NGINX Gateway must have a unique corresponding GatewayClass resource. (default "")
 ```
 
-Provisioner is not meant to be used in production yet (see this issue for more details
+> Note: Provisioner is not ready for production yet (see this issue for more details
 https://github.com/nginxinc/nginx-kubernetes-gateway/issues/634). However, it can be used in the Gateway API conformance
 tests, which expect a Gateway API implementation to provision an independent data plane per Gateway.
 
+> Note: Provisioner uses [this manifest](/deploy/manifests/deployment.yaml) to create an NKG static mode Deployment.
+This manifest gets included into the NKG binary during the NKG build. To customize the Deployment, modify the manifest 
+and **re-build** NKG.
+
 How to deploy:
 
 1. Follow the [installation](/docs/installation.md) instructions up until the Deploy the NGINX Kubernetes Gateway Step