Update `oauthenticator` to latest stable (16.2.1)

Reference Issues or PRs

Relates to https://github.com/nebari-dev/nebari/issues/2308

This is a smaller ask than updating to unreleased version (as in https://github.com/nebari-dev/nebari-docker-images/pull/127) but still gets use over 2 years of patches - including some deprecations/minor changes which will need to be reflected in the nebari codebase.

What does this implement/fix?

Put a x in the boxes that apply

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds a feature)
[ ] Breaking change (fix or feature that would cause existing features not to work as expected)
[ ] Documentation Update
[ ] Code style update (formatting, renaming)
[ ] Refactoring (no functional changes, no API changes)
[ ] Build related changes
[ ] Other (please describe):

Testing

[x] Did you test the pull request locally?
[ ] Did you add new tests?

Documentation

Access-centered content checklist

Text styling

[ ] The content is written with plain language (where relevant).
[ ] If there are headers, they use the proper header tags (with only one level-one header: H1 or # in markdown).
[ ] All links describe where they link to (for example, check the Nebari website).
[ ] This content adheres to the Nebari style guides.

Non-text content

[ ] All content is represented as text (for example, images need alt text, and videos need captions or descriptive transcripts).
[ ] If there are emojis, there are not more than three in a row.
[ ] Don't use flashing GIFs or videos.
[ ] If the content were to be read as plain text, it still makes sense, and no information is missing.

nebari-dev / nebari-docker-images

Update `oauthenticator` to latest stable (16.2.1) #128