chore(deps-dev): bump postcss from 8.4.19 to 8.4.31 in /packages/core

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.19 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@8.4.19...8.4.31)

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

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

packages/core/package.json

@@ -90,7 +90,7 @@
     "@types/nodemailer": "6.4.6",
     "@types/react": "18.0.37",
     "autoprefixer": "10.4.13",
-    "postcss": "8.4.19",
+    "postcss": "8.4.31",
     "postcss-nested": "6.0.0"
   }
 }