deps: bump gatsby-source-filesystem from 5.12.0 to 5.12.1

Bumps [gatsby-source-filesystem](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-source-filesystem) from 5.12.0 to 5.12.1. - [Release notes](https://github.com/gatsbyjs/gatsby/releases) - [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-source-filesystem/CHANGELOG.md) - [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-source-filesystem@5.12.1/packages/gatsby-source-filesystem) --- updated-dependencies: - dependency-name: gatsby-source-filesystem dependency-type: direct:production update-type: version-update:semver-patch ... Signed-off-by: dependabot[bot] <support@github.com>