docs: update argument type for .contains to match impl

[danmana]

See discussion in DefinitelyTyped/DefinitelyTyped#56461

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.31%. Comparing base (c8c74a4) to head (7db06de).
⚠️ Report is 67 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2540   +/-   ##
=======================================
  Coverage   96.31%   96.31%           
=======================================
  Files          49       49           
  Lines        4207     4207           
  Branches     1130     1130           
=======================================
  Hits         4052     4052           
  Misses        155      155           

☔ View full report in Codecov by Harness.
📢 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.