Update to new Mozilla Foundation domain (#16281)

[janriokrause]

Simple search/replace from foundation.mozilla.org to mozillafoundation.org.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.00%. Comparing base (192015c) to head (2db6959).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #16868   +/-   ##
=======================================
  Coverage   80.00%   80.00%           
=======================================
  Files         161      161           
  Lines        8777     8777           
=======================================
  Hits         7022     7022           
  Misses       1755     1755           

☔ 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.