Bump postcss from 8.5.5 to 8.5.6 (#2288)

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.5 to 8.5.6.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](postcss/postcss@8.5.5...8.5.6)

---
updated-dependencies:
- dependency-name: postcss
  dependency-version: 8.5.6
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

package-lock.json

@@ -13,7 +13,7 @@
     "plugins-directory": "node ./cmd/index.mjs"
   },
   "devDependencies": {
-    "postcss": "^8.5.5",
+    "postcss": "^8.5.6",
     "postcss-cli": "^11.0.1",
     "postcss-import": "^16.1.0",
     "postcss-preset-env": "^10.2.3"