Correct version number reference.

[freakboy3742]

Noticed this after publishing the Toga 0.5.1 wheels.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[mhsmith]

Could we replace this with a link to https://devguide.python.org/versions/ so we don't need to update it every year?

[freakboy3742]

Could we replace this with a link to https://devguide.python.org/versions/ so we don't need to update it every year?

I agree that it's problematic to have to remember to update this every time we bump the minimum Python version. However, there's a bunch of other places that we need to do that bump (including pyproject.toml, which provides a formal declaration.

However, It's not strictly "supported Python version" - it definitely tracks very closely to that, but we dropped 3.7 support aa few months before 3.7 was formally dropped. The 3.8 deprecation wasn't closer, but still wasn't exactly the same as the formal EOL date.

There's also the fact that it's public facing documentation.

If anything, I'd suggest we should drop the line entirely. It exists mostly for historical purposes to make it clear that Python 2 isn't supported; that isn't a practical consideration any more, and properties like the version shield, pyproject.toml requires and classifier declarations are now a much more practical representation of version requirements.

[mhsmith]

Yes, I think dropping it entirely would make sense. This would also apply to the other READMEs in the repository.

[freakboy3742]

I've removed all the in-document references to Python versions, in favor of shields on every project, and a couple of related consistency cleanups.