web: bump postcss from 8.4.29 to 8.4.31 in /web (#7064)

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.29 to 8.4.31.
- [Release notes](https://github.com/postcss/postcss/releases)
- [Changelog](https://github.com/postcss/postcss/blob/main/CHANGELOG.md)
- [Commits](https://github.com/postcss/postcss/compare/8.4.29...8.4.31)

---
updated-dependencies:
- dependency-name: postcss
  dependency-type: indirect
...

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

web/package-lock.json

@@ -19153,9 +19153,9 @@
             }
         },
         "node_modules/postcss": {
-            "version": "8.4.29",
-            "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.29.tgz",
-            "integrity": "sha512-cbI+jaqIeu/VGqXEarWkRCCffhjgXc0qjBtXpqJhTBohMUjUQnbBr0xqX3vEKudc4iviTewcJo5ajcec5+wdJw==",
+            "version": "8.4.31",
+            "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.31.tgz",
+            "integrity": "sha512-PS08Iboia9mts/2ygV3eLpY5ghnUcfLV/EXTOW1E2qYxJKGGBUtNjN76FYHnMs36RmARn41bC0AZmn+rR0OVpQ==",
             "dev": true,
             "funding": [
                 {