Bump autoprefixer from 10.4.19 to 10.4.20 in /frontend

Bumps [autoprefixer](https://github.com/postcss/autoprefixer) from 10.4.19 to 10.4.20.
- [Release notes](https://github.com/postcss/autoprefixer/releases)
- [Changelog](https://github.com/postcss/autoprefixer/blob/main/CHANGELOG.md)
- [Commits](postcss/autoprefixer@10.4.19...10.4.20)

---
updated-dependencies:
- dependency-name: autoprefixer
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

frontend/package.json

@@ -7,7 +7,7 @@
   },
   "type": "module",
   "devDependencies": {
-    "autoprefixer": "^10.4.19",
+    "autoprefixer": "^10.4.20",
     "postcss": "^8.4.40",
     "solid-start-node": "^0.3.11",
     "tailwindcss": "^3.4.7",