Relax python six dependency to allow 1.16

[BioGeek]

Changelog: (Fix): Relax python six dependency to allow 1.16
Docs: N/A

The diff between six-1.15.0 and six-1.16.0 only contains some fixes to support Python 3.10 (fixes issues #341, #343 and #349) and shouldn't affect any conan logic.

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• I've read the Contributing guide.
• I've followed the PEP8 style guides for Python code.
• I've opened another PR in the Conan docs repo to the develop branch, documenting this one. -> Not Applicable

^{Note: By default this PR will skip the slower tests and will use a limited set of python versions. Check here how to increase the testing level by writing some tags in the current PR body text.}