Bump @storybook/addon-a11y in /extensions/ql-vscode (github#3364)

Bumps [@storybook/addon-a11y](https://github.com/storybookjs/storybook/tree/HEAD/code/addons/a11y) from 7.6.13 to 7.6.15.
- [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/v7.6.15/code/addons/a11y)

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

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Author: dependabot[bot]

extensions/ql-vscode/package-lock.json

@@ -1972,7 +1972,7 @@
     "@github/markdownlint-github": "^0.6.0",
     "@octokit/plugin-throttling": "^8.0.0",
     "@playwright/test": "^1.40.1",
-    "@storybook/addon-a11y": "^7.6.13",
+    "@storybook/addon-a11y": "^7.6.15",
     "@storybook/addon-actions": "^7.1.0",
     "@storybook/addon-essentials": "^7.1.0",
     "@storybook/addon-interactions": "^7.1.0",