Bump postcss from 8.4.28 to 8.4.31 in /frontend

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.28 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/8.4.28...8.4.31)

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

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

frontend/package.json

@@ -18,7 +18,7 @@
 		"eslint": "^8.28.0",
 		"eslint-config-prettier": "^8.5.0",
 		"eslint-plugin-svelte": "^2.30.0",
-		"postcss": "^8.4.28",
+		"postcss": "^8.4.31",
 		"prettier": "^2.8.0",
 		"prettier-plugin-svelte": "^2.10.1",
 		"svelte": "^4.0.5",

frontend/yarn.lock

@@ -1435,10 +1435,10 @@ postcss-value-parser@^4.0.0, postcss-value-parser@^4.2.0:
   resolved "https://registry.npmjs.org/postcss-value-parser/-/postcss-value-parser-4.2.0.tgz"
   integrity sha512-1NNCs6uurfkVbeXG4S8JFT9t19m45ICnif8zWLd5oPSZ50QnwMfK+H3jv408d4jw/7Bttv5axS5IiHoLaVNHeQ==
 
-postcss@^8, postcss@^8.4.23, postcss@^8.4.25, postcss@^8.4.27, postcss@^8.4.28, postcss@^8.4.5:
-  version "8.4.28"
-  resolved "https://registry.npmjs.org/postcss/-/postcss-8.4.28.tgz"
-  integrity sha512-Z7V5j0cq8oEKyejIKfpD8b4eBy9cwW2JWPk0+fB1HOAMsfHbnAXLLS+PfVWlzMSLQaWttKDt607I0XHmpE67Vw==
+postcss@^8, postcss@^8.4.23, postcss@^8.4.25, postcss@^8.4.27, postcss@^8.4.31, postcss@^8.4.5:
+  version "8.4.31"
+  resolved "https://registry.yarnpkg.com/postcss/-/postcss-8.4.31.tgz#92b451050a9f914da6755af352bdc0192508656d"
+  integrity sha512-PS08Iboia9mts/2ygV3eLpY5ghnUcfLV/EXTOW1E2qYxJKGGBUtNjN76FYHnMs36RmARn41bC0AZmn+rR0OVpQ==
   dependencies:
     nanoid "^3.3.6"
     picocolors "^1.0.0"