chore(deps): bump gatsby-transformer-remark from 6.14.0 to 6.15.0 (#839)

Bumps [gatsby-transformer-remark](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-transformer-remark) from 6.14.0 to 6.15.0.
- [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/[email protected]/packages/gatsby-transformer-remark)

---
updated-dependencies:
- dependency-name: gatsby-transformer-remark
  dependency-version: 6.15.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

package-lock.json

@@ -36,7 +36,7 @@
     "gatsby-remark-prismjs": "^7.15.0",
     "gatsby-source-filesystem": "^5.15.0",
     "gatsby-transformer-json": "^5.15.0",
-    "gatsby-transformer-remark": "^6.13.1",
+    "gatsby-transformer-remark": "^6.15.0",
     "gatsby-transformer-sharp": "^5.15.0",
     "jquery": "^3.7.1",
     "nickel-repl": "file:nickel-repl",