Cross-reference experiments API page
What does this MR do and why?
Closes out https://gitlab.com/gitlab-org/gitlab/-/issues/323514 by cross-linking the experiments API page from the development/experiment_guide.md
page.
Closes out https://gitlab.com/gitlab-org/gitlab/-/issues/323514 by cross-linking the experiments API page from the development/experiment_guide.md
page.