gh-actions: remove one last usage of the now-deprecated Ubuntu 20.04

[mr-c]

No description provided.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.71%. Comparing base (a1de5fa) to head (799eae4).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2097   +/-   ##
=======================================
  Coverage   84.71%   84.71%           
=======================================
  Files          46       46           
  Lines        8359     8359           
  Branches     1960     1960           
=======================================
  Hits         7081     7081           
  Misses        810      810           
  Partials      468      468           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.