BUG: version string parsing in sphinx build

This was never brought up to speed when we switched from using `.post`-formatted versions to `.dev`. https://github.com/natcap/invest.users-guide/blob/c3b2e53c19168a56dc7fb06c4cd0b171be3bc35e/source/conf.py#L57 It still works when building only in the context of this repo. But when building in the context of the invest repo, it gets a version string that can't be associated with a specific tag using `git tag --points-at '3.17.3.dev97+g5081c4005'` because the `3.17.3` tag (and release) does not exist yet. However, userguide builds in invest GHA workflows are still working. And it may simply be working by coincidence: ``` Traceback (most recent call last): File "D:\a\invest\invest\setup.py", line 6, in <module> from Cython.Build import cythonize ModuleNotFoundError: No module named 'Cython' ``` https://github.com/natcap/invest/actions/runs/21368912963/job/61519680788 This error when running `python setup.py --version` may simply cause the program to divert into the `except` clause and treat the build process as if it was happening in the userguide repo instead of the invest repo.