build(deps-dev): bump postcss from 8.4.38 to 8.4.39

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.38 to 8.4.39.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.4.38...8.4.39)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

package.json

@@ -3,7 +3,7 @@
     "@netlify/plugin-lighthouse": "^6.0.0",
     "autoprefixer": "^10.4.19",
     "netlify-plugin-hugo-cache-resources": "^0.2.1",
-    "postcss": "^8.4.38",
+    "postcss": "^8.4.39",
     "postcss-cli": "^11.0.0",
     "postcss-color-mod-function": "^3.0.3"
   }