chore(deps-dev): bump postcss in /packages/sharec-docs

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.7 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@8.4.7...8.4.31)

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

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

Author: dependabot[bot]

packages/sharec-docs/package-lock.json

@@ -52,7 +52,7 @@
     "gulp-svgmin": "^4.1.0",
     "gulp-svgstore": "^9.0.0",
     "markdown-it": "^12.3.2",
-    "postcss": "^8.4.7",
+    "postcss": "^8.4.31",
     "postcss-import": "^14.0.2",
     "postcss-nested": "^5.0.6",
     "rimraf": "^3.0.2",