Merge branch 'docs-serverless-template' into 'master'

Fix serverless.yml template indentation

See merge request gitlab-org/gitlab-ce!24548

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

@@ -121,9 +121,9 @@ In order to deploy functions to your Knative instance, the following files must
        runtime: https://gitlab.com/triggermesh/runtimes/raw/master/nodejs.yaml
        description: "echo function using node.js runtime"
        buildargs:
-         - DIRECTORY=echo
-     environment:
-       FUNCTION: echo
+        - DIRECTORY=echo
+       environment:
+        FUNCTION: echo
    ```