refactor: rename dropdownContentRole to ariaRole

[mxschll]

Description

This PR refactors the dropdownContentRole prop of the Dropdown component to be named ariaRole, aligning its API with other components such as Flashbar.

Related

[Quip proposal: RGJgABPXohP8RGJgABPXohP8]

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 97.24%. Comparing base (9fc78ce) to head (6adf268).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4248      +/-   ##
==========================================
+ Coverage   97.19%   97.24%   +0.04%     
==========================================
  Files         886      886              
  Lines       26021    26040      +19     
  Branches     9433     9435       +2     
==========================================
+ Hits        25291    25322      +31     
+ Misses        724      712      -12     
  Partials        6        6              

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