Bump gatsby-transformer-remark from 2.8.8 to 2.8.25

Bumps [gatsby-transformer-remark](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-transformer-remark) from 2.8.8 to 2.8.25.
- [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@2.8.25/packages/gatsby-transformer-remark)

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

Author: dependabot-preview[bot]

package-lock.json

@@ -51,7 +51,7 @@
     "gatsby-remark-images": "^3.3.8",
     "gatsby-remark-responsive-iframe": "^2.4.3",
     "gatsby-source-filesystem": "^2.3.8",
-    "gatsby-transformer-remark": "^2.8.8",
+    "gatsby-transformer-remark": "^2.8.25",
     "gatsby-transformer-sharp": "^2.5.5",
     "moment": "^2.26.0",
     "node-sass": "^4.14.1",