Try sphinx 6.2.1

[cisaacstern]

Dependabot keeps suggesting we upgrade sphinx (e.g. #592), and docs builds lately fail on those PRs, so I've been closing them.

I know we can have Dependabot ignore sphinx upgrades, but before we do that, I wanted to see if we can bump to this version, because we admittedly are on a quite old sphinx version currently.

I've chosen 6.2.1 because its the latest version in the 6.. series, and our base theme, sphinx-book-theme, supports <7.

Presumably the first build will fail here due to incompatibility with other pinned docs requirements. I'll clean that up in a follow-on commit here.

[cisaacstern]

This is failing with

The conflict is caused by:
    The user requested sphinx==6.2.1
    pangeo-sphinx-book-theme 0.2 depends on sphinx
    myst-parser 0.13.6 depends on sphinx<4 and >=2

so seems like it would require a fix in https://github.com/pangeo-forge/pangeo-sphinx-book-theme/

[cisaacstern]

so seems like it would require a fix in https://github.com/pangeo-forge/pangeo-sphinx-book-theme/

I misunderstood the error. Deeper dive on this locally leaves me to conclude that myst-nb/myst-parser interactions are a bit of a blocker here, so I think we should pause on this until #569 is complete, at which point I think we can drop myst-nb.

[cisaacstern]

Closing as a failed experiment.