Bump postcss from 8.4.6 to 8.4.31 in /ui-tests (#1275)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.6 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@8.4.6...8.4.31)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: indirect
...

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

ui-tests/yarn.lock

@@ -2036,16 +2036,11 @@ ms@^2.1.1:
   resolved "https://registry.yarnpkg.com/ms/-/ms-2.1.3.tgz#574c8138ce1d2b5861f0b44579dbadd60c6615b2"
   integrity sha512-6FlzubTLZG3J2a/NVCAleEhjzq5oxgHyaCU9yYXvcLsvoVaHJq/s5xXI6/XXP6tz7R9xAOtHnSO/tXtF3WRTlA==
 
-nanoid@^3.1.23:
+nanoid@^3.1.23, nanoid@^3.3.6:
   version "3.3.6"
   resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.3.6.tgz#443380c856d6e9f9824267d960b4236ad583ea4c"
   integrity sha512-BGcqMMJuToF7i1rt+2PWSNVnWIkGCU78jBG3RxO/bZlnZPK2Cmi2QaffxGO/2RvWi9sL+FAiRiXMgsyxQ1DIDA==
 
-nanoid@^3.2.0:
-  version "3.2.0"
-  resolved "https://registry.yarnpkg.com/nanoid/-/nanoid-3.2.0.tgz#62667522da6673971cca916a6d3eff3f415ff80c"
-  integrity sha512-fmsZYa9lpn69Ad5eDn7FMcnnSR+8R34W9qJEijxYhTbfOWzr22n1QxCMzXLK+ODyW2973V3Fux959iQoUxzUIA==
-
 napi-macros@~2.0.0:
   version "2.0.0"
   resolved "https://registry.yarnpkg.com/napi-macros/-/napi-macros-2.0.0.tgz#2b6bae421e7b96eb687aa6c77a7858640670001b"
@@ -2146,11 +2141,11 @@ portfinder@^1.0.25:
     mkdirp "^0.5.5"
 
 postcss@^8.3.11:
-  version "8.4.6"
-  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.6.tgz#c5ff3c3c457a23864f32cb45ac9b741498a09ae1"
-  integrity sha512-OovjwIzs9Te46vlEx7+uXB0PLijpwjXGKXjVGGPIGubGpq7uh5Xgf6D6FiJ/SzJMBosHDp6a2hiXOS97iBXcaA==
+  version "8.4.31"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.31.tgz#92b451050a9f914da6755af352bdc0192508656d"
+  integrity sha512-PS08Iboia9mts/2ygV3eLpY5ghnUcfLV/EXTOW1E2qYxJKGGBUtNjN76FYHnMs36RmARn41bC0AZmn+rR0OVpQ==
   dependencies:
-    nanoid "^3.2.0"
+    nanoid "^3.3.6"
     picocolors "^1.0.0"
     source-map-js "^1.0.2"