Bump postcss from 8.4.21 to 8.4.31 (#897)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.21 to 8.4.31.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.4.21...8.4.31)

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

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

apps/web/package.json

@@ -52,7 +52,7 @@
     "next-i18next": "^13.0.3",
     "next-seo": "^5.15.0",
     "php-serialize": "^4.1.1",
-    "postcss": "^8.4.21",
+    "postcss": "^8.4.31",
     "posthog-js": "^1.57.2",
     "react-big-calendar": "^1.8.1",
     "react-hook-form": "^7.42.1",