test: Update tests for ResizeObserver polyfill removal

[TrevorBurnham]

Description

@just-boris noticed test failures when he did a dry run against cloudscape-design/component-toolkit#154, which removes the ResizeObserver polyfill used by the useResizeObserver hook. This PR updates the affected tests to make them compatible with that change.

How has this been tested?

I ran the unit test against the component-toolkit changes locally. I was unable to run the integration test, but @just-boris reported that the issue was that 3 resize observations occurred instead of 2. As he described it, the purpose of the assertion is to prevent infinite resize loops.

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 97.21%. Comparing base (08da1c8) to head (6109e57).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3867   +/-   ##
=======================================
  Coverage   97.21%   97.21%           
=======================================
  Files         844      844           
  Lines       24561    24561           
  Branches     8660     8661    +1     
=======================================
  Hits        23877    23877           
+ Misses        677      635   -42     
- Partials        7       49   +42     

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