test: fill in test coverage for comments.ts

[JoshuaKGoldberg]

PR Checklist

• Addresses an existing open issue: fixes 🧪 Tests: Add tests for remaining functions in src/comments.ts #14
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

Raises test coverage by about 3%.

Also removes a isTsVersionAtLeast that's unnecessary as of #531.

💖

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.98%. Comparing base (de2274d) to head (8cac664).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #609      +/-   ##
==========================================
+ Coverage   76.26%   76.98%   +0.71%     
==========================================
  Files          50       50              
  Lines        4946     4979      +33     
  Branches      663      680      +17     
==========================================
+ Hits         3772     3833      +61     
+ Misses       1173     1145      -28     
  Partials        1        1              

Flag	Coverage Δ
4.8.4	74.33% <100.00%> (+0.73%)	⬆️
latest	76.56% <100.00%> (+0.72%)	⬆️

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