chore(deps-dev): bump @storybook/addon-a11y from 8.2.6 to 8.4.0

Bumps [@storybook/addon-a11y](https://github.com/storybookjs/storybook/tree/HEAD/code/addons/a11y) from 8.2.6 to 8.4.0.
- [Release notes](https://github.com/storybookjs/storybook/releases)
- [Changelog](https://github.com/storybookjs/storybook/blob/next/CHANGELOG.md)
- [Commits](https://github.com/storybookjs/storybook/commits/v8.4.0/code/addons/a11y)

---
updated-dependencies:
- dependency-name: "@storybook/addon-a11y"
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>