Bump @storybook/test-runner from 0.20.1 to 0.21.0 in the storybook group

Bumps the storybook group with 1 update: [@storybook/test-runner](https://github.com/storybookjs/test-runner).


Updates `@storybook/test-runner` from 0.20.1 to 0.21.0
- [Release notes](https://github.com/storybookjs/test-runner/releases)
- [Changelog](https://github.com/storybookjs/test-runner/blob/v0.21.0/CHANGELOG.md)
- [Commits](storybookjs/test-runner@v0.20.1...v0.21.0)

---
updated-dependencies:
- dependency-name: "@storybook/test-runner"
  dependency-type: direct:development
  update-type: version-update:semver-minor
  dependency-group: storybook
...

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

package.json

@@ -100,7 +100,7 @@
     "@storybook/preview-api": "^8.4.7",
     "@storybook/react-vite": "^8.4.7",
     "@storybook/test": "^8.3.1",
-    "@storybook/test-runner": "^0.20.1",
+    "@storybook/test-runner": "^0.21.0",
     "@storybook/theming": "^8.3.1",
     "@svgr/cli": "^8.1.0",
     "@testing-library/react": "^16.1.0",