CI version updates

[rossbar]

Two minor updates to the CI:

1. Add Python3.14 to the default (i.e. latest sphinx) testing matrix
2. Add the --pre flag to the job named "prerelease"

I suspect number 2 was intended - regardless, it's definitely worthwhile to test against sphinx rc's in particular.

There are more extensive CI changes that I think are worthwhile - for example, the testing matrix for old sphinx versions include sphinx/Python combos for which there are no wheels (e.g. sphinx v6 only supplies wheels up to Python3.11, but we test with 3.12 and 3.13 there too). Such changes might warrant more discussion so I'll save them for a separate PR - the two changes should be uncontroversial.

[stefanv]

Is this just to catch pre-releases on pypi, or would you prefer to pull from the Nightly Wheels? Either way is fine, changes look good :)

[rossbar]

The most important dependency to catch (IMO) is sphinx - that's really where numpydoc would benefit from dev-testing to ensure that sphinx changes don't break the extension. AFAIK there are no sphinx nightlies, so catching the RC's is as good as we can do for now!

[stefanv]

There are more extensive CI changes that I think are worthwhile - for example, the testing matrix for old sphinx versions include sphinx/Python combos for which there are no wheels (e.g. sphinx v6 only supplies wheels up to Python3.11, but we test with 3.12 and 3.13 there too). Such changes might warrant more discussion so I'll save them for a separate PR - the two changes should be uncontroversial.

I don't think that's controversial, FWIW.

[stefanv]

Thanks!