chore(deps): bump gatsby-plugin-mdx from 3.4.0 to 3.15.2

Bumps [gatsby-plugin-mdx](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-mdx) from 3.4.0 to 3.15.2.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-mdx/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/[email protected]/packages/gatsby-plugin-mdx)

---
updated-dependencies:
- dependency-name: gatsby-plugin-mdx
  dependency-version: 3.15.2
  dependency-type: direct:production
...

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

Author: dependabot[bot]

package.json

@@ -18,7 +18,7 @@
     "date-fns": "^2.17.0",
     "gatsby": "4.25.2",
     "gatsby-plugin-manifest": "4.25.0",
-    "gatsby-plugin-mdx": "3.4.0",
+    "gatsby-plugin-mdx": "3.15.2",
     "gatsby-plugin-netlify": "^5.1.1",
     "gatsby-plugin-react-helmet": "^5.4.0",
     "gatsby-plugin-sharp": "4.25.0",