chore(deps-dev): bump postcss from 8.5.3 to 8.5.4 in the postcss group

Bumps the postcss group with 1 update: [postcss](https://github.com/postcss/postcss).


Updates `postcss` from 8.5.3 to 8.5.4
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.3...8.5.4)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.4
  dependency-type: direct:development
  update-type: version-update:semver-patch
  dependency-group: postcss
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

package-lock.json

@@ -74,7 +74,7 @@
     "lightningcss": "^1.30.0",
     "lockfile-lint": "^4.14.1",
     "open": "^10.1.2",
-    "postcss": "^8.5.3",
+    "postcss": "^8.5.6",
     "postcss-cli": "^11.0.1",
     "prettier": "^3.5.3",
     "prettier-plugin-astro": "^0.14.1",