build(deps): bump @mdx-js/mdx from 1.6.18 to 1.6.22 in /docs

Bumps [@mdx-js/mdx](https://github.com/mdx-js/mdx) from 1.6.18 to 1.6.22.
- [Release notes](https://github.com/mdx-js/mdx/releases)
- [Changelog](https://github.com/mdx-js/mdx/blob/main/changelog.md)
- [Commits](mdx-js/mdx@v1.6.18...v1.6.22)

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

Author: dependabot[bot]

docs/package-lock.json

@@ -8,7 +8,7 @@
   "dependencies": {
     "@emotion/core": "^10.0.35",
     "@emotion/styled": "^10.0.27",
-    "@mdx-js/mdx": "^1.6.18",
+    "@mdx-js/mdx": "^1.6.22",
     "@mdx-js/react": "^1.6.16",
     "emotion-theming": "^10.0.27",
     "gatsby": "^2.24.65",