chore: bump postcss from 8.4.27 to 8.4.31 in /pwa (#338)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.27 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@8.4.27...8.4.31)

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

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

Author: dependabot[bot]

pwa/package.json

@@ -20,7 +20,7 @@
     "isomorphic-unfetch": "^4.0.2",
     "next": "13.4.11",
     "next-auth": "^4.23.1",
-    "postcss": "8.4.27",
+    "postcss": "8.4.31",
     "ra-i18n-polyglot": "^4.14.1",
     "ra-language-english": "^4.14.1",
     "ra-language-french": "^4.14.1",