build(deps): lock min Python version to 3.7.9

[tombh]

Github Actions for windows uses Python 3.7.9 not 3.7.16. This wasn't picked up in the PR that introduced the original lock because of dependency caching. See:

https://github.com/openlawlibrary/pygls/actions/runs/5702563535/job/15454396739#step:6:12

Code review checklist (for code reviewer to complete)

• [ ] Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• [ ] Title summarizes what is changing
• [ ] Commit messages are meaningful (see this for details)
• [ ] Tests have been included and/or updated, as appropriate
• [ ] Docstrings have been included and/or updated, as appropriate
• [ ] Standalone docs have been updated accordingly

[tombh]

Oh! You already approved it, thank you 🙇