Bump @mdx-js/mdx from 1.6.22 to 3.0.0

Bumps [@mdx-js/mdx](https://github.com/mdx-js/mdx/tree/HEAD/packages/mdx) from 1.6.22 to 3.0.0.
- [Release notes](https://github.com/mdx-js/mdx/releases)
- [Changelog](https://github.com/mdx-js/mdx/blob/main/changelog.md)
- [Commits](https://github.com/mdx-js/mdx/commits/3.0.0/packages/mdx)

---
updated-dependencies:
- dependency-name: "@mdx-js/mdx"
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

packages/gatsby-mdx/package.json

@@ -4,7 +4,7 @@
 	"version": "1.0.0",
 	"author": "Chris Biscardi <chris@christopherbiscardi.com>",
 	"dependencies": {
-		"@mdx-js/mdx": "^1.0.10",
+		"@mdx-js/mdx": "^3.0.0",
 		"@mdx-js/react": "^1.0.6",
 		"@mdx-js/tag": "^0.20.3",
 		"babel-plugin-styled-components": "^1.10.0",