refactor: rename children prop to content

[mxschll]

Description

This PR refactors the children prop of the Dropdown component to be named content, aligning its API with other components such as Tooltip and Popover.

Related

[Quip proposal: RGJgABPXohP8RGJgABPXohP8]

How has this been tested?

Unit tests and regression tests are green.

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 97.19%. Comparing base (9a1b7c5) to head (ec7b3dd).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4229   +/-   ##
=======================================
  Coverage   97.19%   97.19%           
=======================================
  Files         886      886           
  Lines       26006    26008    +2     
  Branches     9419     9422    +3     
=======================================
+ Hits        25276    25278    +2     
+ Misses        724      683   -41     
- Partials        6       47   +41     

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