Update CI-tested Python3 versions

[petiepooo]

Remove python v3.6 and add v3.10

[petiepooo]

That was not so smooth..
As a float, 3.10 == 3.1, so trying to add 3.10 unquoted attempted to use python 3.1. Quoting 3.10 so it was treated as a string instead of a float worked.
Also, unfortunately, mox is using the inspect.getargspec() function, which is deprecated and has been removed in python 3.11. Until that is updated, the testing framework does not work.
For consistency, all python versions are now quoted, since semantic version numbers are strings, not floats.
I think this patch is ready, and should also fix the failure seen in #43