Bump postcss from 8.4.24 to 8.4.31

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.24 to 8.4.31.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.4.24...8.4.31)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: direct:production
...

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

Author: dependabot[bot]

package-lock.json

@@ -52,7 +52,7 @@
     "grunt": "^1.6.1",
     "grunt-contrib-clean": "^2.0.1",
     "grunt-contrib-uglify": "^5.2.2",
-    "postcss": "^8.4.24",
+    "postcss": "^8.4.31",
     "postcss-cli": "^10.1.0",
     "postcss-import": "^15.1.0",
     "postcss-nesting": "^11.2.2",