Remove files related to Vercel deployments

[remcohaszing]

Initial checklist

• I read the support docs
• I read the contributing guide
• I agree to follow the code of conduct
• I searched issues and discussions and couldn’t find anything or linked relevant results below
• I made sure the docs are up to date
• I included tests (or that’s not needed)

Description of changes

We don’t deploy to Vercel. We use GitHub Pages.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (af23c2d) to head (a4a60f0).

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #2669   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           21        21           
  Lines         2649      2649           
  Branches         2         2           
=========================================
  Hits          2649      2649           

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