docs: run rst2myst

[consideRatio]

No open PRs should have conflicts with this as verified by checking for changes to rST files in open PRs, using a script @minrk created.

# pip install pygithub
from github import Github as GitHub

gh = GitHub()

repo = gh.get_repo("jupyterhub/kubespawner")
for pull in repo.get_pulls(state="open"):
    pull_files = [f.filename for f in list(pull.get_files())]
    if any(f.endswith(".rst") for f in pull_files):
        print(f"- [ ] #{pull.number}:")
        for f in pull_files:
            if f.endswith(".rst"):
                print(f"  - {f}")
        continue

[GeorgianaElena]

Thanks @consideRatio 🚀 !

[consideRatio]

Thank you for the merge @GeorgianaElena!!! ❤️ 🎉 🌻!