Remove pinning of pydocstyle

[MarkusPiotrowski]

With the recent update of flake8-docstring, pinning of pydocstyle to versions < 4.0.0 should no longer be necessary (https://gitlab.com/pycqa/flake8-docstrings/issues/36).

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[peterjc]

Assuming the tests pass, this looks good.

[MarkusPiotrowski]

There are now numerous D413 (missing blank line after last section) and some D412 (no blank lines allowed between a section header and its content) issues now. Need to investigate.
A quick inspection let suggest that D413 is reported if the docstring ends with single line 'section'.

[peterjc]

D413 is strange, we fixed them back on #1192 - but evidentally pydocstyle have tweaked the rules.

[MarkusPiotrowski]

Reported as issue at PyCQA/pydocstyle#401 (comment).

If we update to pydocstyle versions >3.0.0 we need to (temporarily) ignore D413 and D412, either until pydocstyle changes it rules or until we have solved all these 'issues'.

[peterjc]

I think sticking with the older pydocstyle makes sense, pending some comments on that bug you kindly filed.

[peterjc]

It seems the D413 false positives are fixed in pydocstyle v5 released earlier this month.

We could remove the pinning (as in the original change on #2230), but we now know that v4 does not work for us. Therefore #2414 changes this to require at least v5.

[peterjc]

Superseded by #2414