Bump postcss from 8.4.13 to 8.4.31 in /frontend

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.13 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@8.4.13...8.4.31)

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

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

frontend/package.json

@@ -154,7 +154,7 @@
     "@typescript-eslint/parser": "6.7.0",
     "jest-junit": "8.0.0",
     "mrs-developer": "*",
-    "postcss": "8.4.13",
+    "postcss": "8.4.31",
     "prettier": "3.0.3",
     "razzle": "4.2.18",
     "stylelint": "15.10.3",

frontend/yarn.lock

@@ -14207,7 +14207,7 @@ __metadata:
     "@typescript-eslint/parser": 6.7.0
     jest-junit: 8.0.0
     mrs-developer: "*"
-    postcss: 8.4.13
+    postcss: 8.4.31
     prettier: 3.0.3
     razzle: 4.2.18
     stylelint: 15.10.3
@@ -19392,15 +19392,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"nanoid@npm:^3.3.3":
-  version: 3.3.7
-  resolution: "nanoid@npm:3.3.7"
-  bin:
-    nanoid: bin/nanoid.cjs
-  checksum: d36c427e530713e4ac6567d488b489a36582ef89da1d6d4e3b87eded11eb10d7042a877958c6f104929809b2ab0bafa17652b076cdf84324aa75b30b722204f2
-  languageName: node
-  linkType: hard
-
 "nanoid@npm:^3.3.6":
   version: 3.3.6
   resolution: "nanoid@npm:3.3.6"
@@ -21459,17 +21450,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"postcss@npm:8.4.13":
-  version: 8.4.13
-  resolution: "postcss@npm:8.4.13"
-  dependencies:
-    nanoid: ^3.3.3
-    picocolors: ^1.0.0
-    source-map-js: ^1.0.2
-  checksum: 514fb3552805a5d039a2d6b4df3e73f657001716ca93c0d57e6067b0473abdea70276d80afc96005c9aaff82ed5d98062bd97724d3f47ca400fba0b5e9e436ed
-  languageName: node
-  linkType: hard
-
 "postcss@npm:8.4.31":
   version: 8.4.31
   resolution: "postcss@npm:8.4.31"