www/py-requests: Chase dns/py-idna update

ports r552091 updated idna to 2.10, breaking www/py-requests, and its
dependents, with:

raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'idna<2.9,>=2.5' distribution was not found and is required by requests

Backport an upstream commit [1] that kinda addresses "most" of the root
cause problem of this for future dependency updates, by not pinning on
minor versions.

[1] https://github.com/psf/requests/pull/5342

PR: 245938
Reported by: lbartoletti, ohauer
MFH: 2020Q3
X-MFH-With: 552091