chore: remove references to now-unused util.inherits

[mark-wiemer]

PR Checklist

• Addresses an existing open issue: fixes 🐛 Bug: remove util.inherits / convert to classes #5025
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

A set of previous PRs linked to the backing issue removed all references to this old symbol. Now we can fully remove it to mark the work complete :)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.78%. Comparing base (c3f32ce) to head (bb1543b).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5766      +/-   ##
==========================================
+ Coverage   88.74%   88.78%   +0.03%     
==========================================
  Files          66       66              
  Lines        4744     4742       -2     
  Branches      976      976              
==========================================
  Hits         4210     4210              
+ Misses        534      532       -2     

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[mark-wiemer]

Gonna slow down now and wait for @mochajs/maintenance-crew folks to come back online :)

[JoshuaKGoldberg]

Thus closes out the old inherits saga!