fix: Fixes treeview offset for better items alignment

[pan-kot]

Description

Minor adjustment for tree view so that expand toggles and icons are aligned.

Rel: AWSUI-61584

How has this been tested?

• Existing screenshot tests

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 (2432b15) to head (e76eeac).
⚠️ Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4163   +/-   ##
=======================================
  Coverage   97.14%   97.14%           
=======================================
  Files         873      873           
  Lines       25648    25648           
  Branches     9281     9280    -1     
=======================================
  Hits        24916    24916           
- Misses        685      726   +41     
+ Partials       47        6   -41     

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