Bump postcss from 8.5.3 to 8.5.6

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.3 to 8.5.6.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.3...8.5.6)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.6
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

package-lock.json

@@ -41,7 +41,7 @@
     "hugo-bin": "0.142.0",
     "jquery": "3.7.1",
     "npm-run-all": "4.1.5",
-    "postcss": "8.5.3",
+    "postcss": "8.5.6",
     "postcss-cli": "11.0.1",
     "prettier": "3.5.3",
     "stylelint": "16.21.1",