Bump gatsby-transformer-remark from 2.16.1 to 5.25.1

Bumps [gatsby-transformer-remark](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-transformer-remark) from 2.16.1 to 5.25.1.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-transformer-remark/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-transformer-remark@5.25.1/packages/gatsby-transformer-remark)

---
updated-dependencies:
- dependency-name: gatsby-transformer-remark
  dependency-type: direct:production
...

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

packages/website/package.json

@@ -38,7 +38,7 @@
     "gatsby-remark-responsive-iframe": "^2.2.0",
     "gatsby-source-filesystem": "^2.1.0",
     "gatsby-transformer-json": "^2.2.0",
-    "gatsby-transformer-remark": "^2.5.0",
+    "gatsby-transformer-remark": "^5.25.1",
     "lodash": "^4.17.4",
     "lodash-webpack-plugin": "^0.11.4",
     "prismjs": "^1.16.0",