Temporarily disable check_manifest on MinGW

[darbyjohnston]

This PR removes the MinGW CI job. It seems to have intermittent failures and I don't think we have the resources to troubleshoot it each time:
https://github.com/darbyjohnston/OpenTimelineIO/actions/runs/17500902789/job/49713367017

Edit: Note that this doesn't remove the various fixes for MinGW, just the CI job.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.00%. Comparing base (c0e97b0) to head (619eaaf).
⚠️ Report is 66 commits behind head on main.

❌ Your changes status has failed because you have indirect coverage changes. Learn more about Unexpected Coverage Changes and reasons for indirect coverage changes.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1935      +/-   ##
==========================================
+ Coverage   84.11%   85.00%   +0.88%     
==========================================
  Files         198      181      -17     
  Lines       22241    13074    -9167     
  Branches     4687     1206    -3481     
==========================================
- Hits        18709    11113    -7596     
+ Misses       2610     1778     -832     
+ Partials      922      183     -739     

Flag	Coverage Δ
py-unittests	85.00% <ø> (+0.88%)	⬆️

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see 139 files with indirect coverage changes

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[meshula]

Thanks for addressing this. I agree with your assessment that we lack resources to maintain mingw builds at the moment. Can I suggest we comment it out for 30 days, and post an RFC in OTIO issues and ASWF Slack requesting a maintainer, and if none steps up, we delete it as you propose?

[darbyjohnston]

I looked into it some more, and the part that is failing is the check_manifest step:
https://github.com/mgedmin/check-manifest

I skimmed their PRs and didn't see any related to the error we are seeing, so maybe for now we just disable that step. I updated the PR and added a todo comment to fix it at some point.