chore: Uses updated stsn testing utils

[pan-kot]

Description

Using the utils introduced here: cloudscape-design/component-toolkit#159

Rel: AWSUI-61217

How has this been tested?

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 97.14%. Comparing base (ce7b93a) to head (729b9c7).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3850   +/-   ##
=======================================
  Coverage   97.14%   97.14%           
=======================================
  Files         844      844           
  Lines       24515    24515           
  Branches     8645     8646    +1     
=======================================
  Hits        23815    23815           
+ Misses        693      651   -42     
- Partials        7       49   +42     

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