build(deps): bump gatsby-plugin-mdx from 1.0.56 to 2.14.1

Bumps [gatsby-plugin-mdx](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-mdx) from 1.0.56 to 2.14.1.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/gatsby-plugin-mdx@2.14.1/packages/gatsby-plugin-mdx/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-plugin-mdx@2.14.1/packages/gatsby-plugin-mdx)

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

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

package.json

@@ -24,7 +24,7 @@
     "gatsby": "^2.18.17",
     "gatsby-link": "^2.2.11",
     "gatsby-plugin-catch-links": "^2.1.7",
-    "gatsby-plugin-mdx": "^1.0.36",
+    "gatsby-plugin-mdx": "^2.14.1",
     "gatsby-plugin-react-helmet": "^3.1.6",
     "gatsby-plugin-sass": "^2.1.13",
     "gatsby-plugin-sharp": "^2.2.19",