## Description

Removes references to `ThemeData.primaryColorBrightness`, deprecated in https://github.com/flutter/flutter/pull/93396 and subject to remove now because of our [deprecation policy](https://github.com/flutter/flutter/wiki/Tree-hygiene#deprecations).

## Related PRs
 - https://github.com/flutter/flutter/pull/93396

## Tests
 - Removed unneeded tests, removed references.