Fix mix of string and symbol in graphQL response

The following discussion from gitlab-org/gitlab!118975 (merged) should be addressed:

• @stanhu started a discussion: (+1 comment)

  I'm not sure if we really care, but this mixes symbols and JSON strings:

  > [{:source_url=>"https://docs.gitlab.com/ee/development/pipelines/internals",
    "info"=>"To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/product/ux/technical-writing/#assignments",
    "group"=>"Engineering Productivity",
    "stage"=>"none",
    "source"=>"doc/development/pipelines/internals.md",
    "source_type"=>"doc"},