chore(deps-dev): bump gatsby-source-filesystem from 2.4.1 to 2.4.2

Bumps [gatsby-source-filesystem](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-source-filesystem) from 2.4.1 to 2.4.2.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/gatsby-source-filesystem@2.4.2/packages/gatsby-source-filesystem/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-source-filesystem@2.4.2/packages/gatsby-source-filesystem)

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

package.json

@@ -85,7 +85,7 @@
     "gatsby-plugin-robots-txt": "^1.5.3",
     "gatsby-plugin-sharp": "^2.7.1",
     "gatsby-plugin-sitemap": "^2.5.0",
-    "gatsby-source-filesystem": "^2.4.1",
+    "gatsby-source-filesystem": "^2.4.2",
     "gatsby-transformer-sharp": "^2.5.21",
     "husky": "^4.3.0",
     "identity-obj-proxy": "^3.0.0",