Bump @storybook/addon-a11y from 6.3.6 to 7.6.13 in /webapp

Bumps [@storybook/addon-a11y](https://github.com/storybookjs/storybook/tree/HEAD/code/addons/a11y) from 6.3.6 to 7.6.13.
- [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/v7.6.13/code/addons/a11y)

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

Signed-off-by: dependabot[bot] <support@github.com>

webapp/package.json

@@ -72,7 +72,7 @@
     "@babel/preset-env": "^7.22.4",
     "@faker-js/faker": "5.1.0",
     "@nuxtjs/composition-api": "0.32.0",
-    "@storybook/addon-a11y": "^6.3.6",
+    "@storybook/addon-a11y": "^7.6.13",
     "@storybook/addon-actions": "^5.3.21",
     "@storybook/addon-notes": "^5.3.18",
     "@storybook/vue": "~7.4.0",