fix: Table scrollable detection

[just-boris]

Description

Fixing a regression after resize observer switch: cloudscape-design/component-toolkit#154

Related links, issue #, if available: n/a

How has this been tested?

• Locally
• Because the regression was only in Firefox, not testable in the integration tests. Screenshot tests capture it (that's how the issue was detected)

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.22%. Comparing base (4cb9a71) to head (2ba1862).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3871   +/-   ##
=======================================
  Coverage   97.22%   97.22%           
=======================================
  Files         844      844           
  Lines       24595    24595           
  Branches     8676     8676           
=======================================
  Hits        23913    23913           
  Misses        675      675           
  Partials        7        7           

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