correct dockerfile term and update port

doc/user/project/clusters/serverless/index.md

@@ -61,8 +61,8 @@ To run Knative on Gitlab, you will need:
         - tm -n "$KUBE_NAMESPACE" --config "$KUBECONFIG" deploy service "$CI_PROJECT_NAME" --from-image "$CI_REGISTRY_IMAGE" --wait
     ```
 
-1. **Docker File:** Knative requires a docker file in order to build your application. It should be included 
-    at the root of your project's repo.
+1. **Dockerfile:** Knative requires a Dockerfile in order to build your application. It should be included 
+    at the root of your project's repo and expose port 8080.
 
 ## Installing Knative via GitLab's Kubernetes integration