Bump postcss from 8.4.12 to 8.4.31 (#723)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.12 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@8.4.12...8.4.31)

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

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package.json

@@ -33,7 +33,7 @@
         "less-loader": "^10.2.0",
         "lodash": "^4.17.19",
         "masonry-layout": "^4.2.2",
-        "postcss": "^8.2.1",
+        "postcss": "^8.4.31",
         "postcss-import": "^14.0.1",
         "resolve-url-loader": "^4.0.0",
         "sweetalert2": "^11.3.3",