package/python-requests: relax version dependency on python-idna

The dockerCompose runtime test currently fails with:

pkg_resources.ContextualVersionConflict: (idna 2.9 (/usr/lib/python3.8/site-packages), Requirement.parse('idna<2.9,>=2.5'), {'requests'})

This is due to the fact that the python-requests module has a strict
version dependency on the python-idna module: 'idna>=2.5,<2.9'.

Since Buildroot commit 237d31bf, we're
using python-idna in version 2.9, which no longer matches the version
dependency expressed by python-requests, causing the failure.

Upstream has addressed this issue in commit
https://github.com/psf/requests/commit/c46f55bd48dabc02f033d252f8c64e2011f37361,
which relaxes the version requirement.

Fixes:
https://gitlab.com/buildroot.org/buildroot/-/jobs/498144417



Signed-off-by: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>