Resolve "Document which API is accessible with CI_JOB_TOKEN"

What does this MR do?

Documents what features/API uses CI_JOB_TOKEN for the CE edition.

In https://gitlab.com/gitlab-org/gitlab-ce/issues/48627#note_85531576 @axil suggested moving the section of ### CI job token or parts of it which I don't think will make things more clear since that would lead to ci/triggers linking to ci/variables to understand how to use it which I don't its the scope of ci/variables is.

Related issues

Closes #48627 (closed)

Related MR

gitlab-org/gitlab-ee!6517

Moving docs to a new location?

Read the guidelines: https://docs.gitlab.com/ce/development/writing_documentation.html#changing-document-location

• Make sure the old link is not removed and has its contents replaced with a link to the new location.
• Make sure internal links pointing to the document in question are not broken.
• Search and replace any links referring to old docs in GitLab Rails app, specifically under the app/views/ and ee/app/views (for GitLab EE) directories.
• Make sure to add redirect_from to the new document if there are any Disqus comments on the old document thread.
• If working on CE and the ee-compat-check jobs fails, submit an MR to EE with the changes as well (https://docs.gitlab.com/ce/development/writing_documentation.html#cherry-picking-from-ce-to-ee).
• Ping one of the technical writers for review.