Bump postcss from 8.5.3 to 8.5.6

Bumps [postcss](https://github.com/postcss/postcss) from 8.5.3 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@8.5.3...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]>

Author: dependabot[bot]

package.json

@@ -15,7 +15,7 @@
     "rtlcss": "4.3.0",
     "sass": "1.87.0",
     "npm-run-all2": "8.0.1",
-    "postcss": "8.5.3",
+    "postcss": "8.5.6",
     "postcss-cli": "11.0.1",
     "remark-cli": "12.0.1",
     "remark-lint": "10.0.1",