chore(openshift): remove dead prod/test/dev kustomize overlays

overlays/{prod,test,dev} are not part of any deploy path — the Deploy Instance
workflow renders from overlays/instance-template. They were stale/misleading
(their route patches never reached any cluster). Remove them and repoint the
README's OpenShift deploy snippet at the real mechanism (Deploy Instance /
instance-template).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: alex-struk

README.md

@@ -797,12 +797,12 @@ docker run \
 
 ### OpenShift/Kubernetes
 
-Kubernetes manifests are provided in `deployments/openshift/kustomize/`:
-
-```bash
-# Apply to cluster
-kubectl apply -k deployments/openshift/kustomize/overlays/dev
-```
+Kubernetes manifests are provided in `deployments/openshift/kustomize/`. Deployments are
+driven by the **Deploy Instance** GitHub Actions workflow, which renders an instance-specific
+overlay from `overlays/instance-template` and applies it (pushes to `develop` deploy to
+`fd34fb-test`, pushes to `main` deploy to `fd34fb-prod`). See
+[docs-md/openshift-deployment/AUTO_DEPLOY.md](docs-md/openshift-deployment/AUTO_DEPLOY.md) and
+[docs-md/openshift-deployment/KUSTOMIZE_INSTANCE_TEMPLATE.md](docs-md/openshift-deployment/KUSTOMIZE_INSTANCE_TEMPLATE.md).
 
 **Features:**
 - Database migration init containers