build(deps): bump gatsby-plugin-sass from 6.11.0 to 6.12.0 (#756)

Bumps [gatsby-plugin-sass](https://github.com/gatsbyjs/gatsby/tree/HEAD/packages/gatsby-plugin-sass) from 6.11.0 to 6.12.0.
- [Release notes](https://github.com/gatsbyjs/gatsby/releases)
- [Changelog](https://github.com/gatsbyjs/gatsby/blob/master/packages/gatsby-plugin-sass/CHANGELOG.md)
- [Commits](https://github.com/gatsbyjs/gatsby/commits/gatsby-plugin-sass@6.12.0/packages/gatsby-plugin-sass)

---
updated-dependencies:
- dependency-name: gatsby-plugin-sass
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

package.json

@@ -32,7 +32,7 @@
     "gatsby-plugin-offline": "^6.12.0",
     "gatsby-plugin-react-i18next": "^2.0.5",
     "gatsby-plugin-react-svg": "^3.3.0",
-    "gatsby-plugin-sass": "^6.11.0",
+    "gatsby-plugin-sass": "^6.12.0",
     "gatsby-plugin-sharp": "^5.10.0",
     "gatsby-plugin-sitemap": "^6.11.0",
     "gatsby-remark-autolink-headers": "^6.11.0",