dns/py-idna: Update to 2.10

Update test target directly invoke unittest, as setup.py test is
technically deprecated and discouraged upstream, currently without a
canonical replacement [1]

Changelog:

https://github.com/kjd/idna/blob/v2.10/HISTORY.rst

[1] https://github.com/pypa/setuptools/issues/1684

PR: 245938
Submitted by: Daniel Engberg <daniel.engberg.lists pyret net>
MFH: 2020Q3 (blanket: bugfix releas(es))