keep compatibility with the development version of pint

[keewis]

• closes upstream-dev pint tests are failing #338

Since pint is now capable of parsing % we don't need the workaround anymore, which allows us to stop using pint's internal API.

I'm not sure about the second failure from #338 (ValueError: Invalid format specifier): I can't reproduce that locally.
Edit: that seems to be a race condition, it will only be raised if we execute tests in parallel.

[dcherian]

Thanks!

[keewis]

It seems the version of cf-xarray in CI is 0.1.dev1+g<commit hash>. To fix that, you probably need to pass fetch-depth: 0 to actions/checkout so setuptools-scm can detect the release tags.

At the moment, not fixing this will not cause any issues (besides a slight confusion when reading the logs), but be aware that as soon as a dependency decides to depend on cf-xarray the CI will stop working (we had this issue with xarray and cfgrib).