Removes mention of $AUTO_DEVOPS_DOMAIN in doc

Even though there's no relation to the feature (it's actually about
overriding template values, best to replace this with
$KUBE_INGRESS_BASE_DOMAIN to avoid any potential confusion

doc/ci/yaml/README.md

@@ -1986,7 +1986,7 @@ production:
     - deploy
   environment:
     name: production
-    url: https://$CI_PROJECT_PATH_SLUG.$AUTO_DEVOPS_DOMAIN
+    url: https://$CI_PROJECT_PATH_SLUG.$KUBE_INGRESS_BASE_DOMAIN
   only:
     - master
 ```