Bump postcss from 8.4.24 to 8.4.31 in /ui-tests

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: indirect
...

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

ui-tests/yarn.lock

@@ -3249,13 +3249,13 @@ __metadata:
   linkType: hard
 
 "postcss@npm:^8.3.11":
-  version: 8.4.24
-  resolution: "postcss@npm:8.4.24"
+  version: 8.4.31
+  resolution: "postcss@npm:8.4.31"
   dependencies:
     nanoid: ^3.3.6
     picocolors: ^1.0.0
     source-map-js: ^1.0.2
-  checksum: 814e2126dacfea313588eda09cc99a9b4c26ec55c059188aa7a916d20d26d483483106dc5ff9e560731b59f45c5bb91b945dfadc670aed875cc90ddbbf4e787d
+  checksum: 1d8611341b073143ad90486fcdfeab49edd243377b1f51834dc4f6d028e82ce5190e4f11bb2633276864503654fb7cab28e67abdc0fbf9d1f88cad4a0ff0beea
   languageName: node
   linkType: hard