build(deps): bump gatsby from 4.13.1 to 4.15.2 in /docs (#2895)

Bumps [gatsby](https://github.com/gatsbyjs/gatsby) from 4.13.1 to 4.15.2.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/compare/gatsby@4.13.1...gatsby@4.15.2)

---
updated-dependencies:
- dependency-name: gatsby
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

docs/package.json

@@ -10,7 +10,7 @@
     "@emotion/styled": "^11.8.1",
     "@mdx-js/mdx": "^1.6.22",
     "@mdx-js/react": "^1.6.16",
-    "gatsby": "^4.13.1",
+    "gatsby": "^4.15.2",
     "gatsby-alias-imports": "^1.0.6",
     "gatsby-plugin-canonical-urls": "^4.13.0",
     "gatsby-plugin-catch-links": "^4.13.0",