Don't advertise qpoption in developer docs

docs/.nav.yml

@@ -138,8 +138,6 @@ nav:
           - Configuring certificate class: serving/services/certificate-class.md
           - Configuring custom domains: serving/services/custom-domains.md
           - Using a custom TLS certificate for DomainMapping: serving/services/custom-tls-certificate-domain-mapping.md
-          - Using extensions enabled by QPOptions: serving/services/using-queue-extensions.md
-          # TODO: Add security section to docs?
           - Configure resource requests and limits: serving/services/configure-requests-limits-services.md
           - Configuring probes: serving/services/configure-probing.md
           - Configuring HTTP: serving/services/http-protocol.md
@@ -162,7 +160,6 @@ nav:
         - Configuring the ingress gateway: serving/setting-up-custom-ingress-gateway.md
         - Configuring domain names: serving/using-a-custom-domain.md
         - Converting a Kubernetes Deployment to a Knative Service: serving/convert-deployment-to-knative-service.md
-        - Extending Queue Proxy image with QPOptions: serving/queue-extensions.md
         - Serving configuration:
           - Configure Deployment resources: serving/configuration/deployment.md
           - Configuring gradual rollout of traffic to Revisions: serving/configuration/rolling-out-latest-revision-configmap.md

docs/serving/configuration/feature-flags.md

@@ -439,7 +439,7 @@ spec:
 
 You must set this feature to either "enabled or "allowed" when using QPOptions. The flag controls whether Knative mounts the `pod-info` volume to the `queue-proxy` container.
 
-Mounting the `pod-info` volume allows extensions that use QPOptions to access the Service annotations, by reading the `/etc/podinfo/annnotations` file. See [Extending Queue Proxy image with QPOptions](../queue-extensions.md) for more details.
+Mounting the `pod-info` volume allows extensions that use QPOptions to access the Service annotations, by reading the `/etc/podinfo/annnotations` file. 
 
 When this feature is `enabled`, the `pod-info` volume is always mounted. This is helpful in case where all or most of the cluster Services are required to use extensions that rely on QPOptions.