fix MaixPy submodule url

[luke21m]

What is this PR for?

When starting to work with this project I created a fork of the selfcustody/krux repo and then tried to clone it with git clone --recurse-submodules. This caused an error with MaixPy because it was looking for my fork of MaixPy which did not exist. See error:

remote: Repository not found.
fatal: Authentication failed for 'https://github.com/luke21m/MaixPy/'
fatal: clone of 'https://github.com/luke21m/MaixPy' into submodule path '/Users/luke/krux/firmware/MaixPy' failed
Failed to clone 'firmware/MaixPy' a second time, aborting

Since the other submodules were cloning without me having to manually fork them on github, I changed the MaixPy url in .gitmodules to match. Then it works.

What is the purpose of this pull request?

• [X] Bug fix
• [ ] New feature
• [ ] Docs update
• [ ] Other

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.67%. Comparing base (ff5fa4b) to head (6343a38). Report is 22 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #458 +/- ## ======================================== Coverage 94.67% 94.67% ======================================== Files 70 70 Lines 7575 7575 ======================================== Hits 7172 7172 Misses 403 403 ```

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[odudex]

Thank you Luke! This is from the time I was working exclusively on my private repository, with my custom Maixpy, I ended up forgetting to restore to defaults.