build(deps-dev): bump postcss from 8.4.20 to 8.4.21 in /web

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.20 to 8.4.21.
- [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/8.4.20...8.4.21)

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

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

web/package-lock.json

@@ -41,7 +41,7 @@
         "netlify-plugin-cypress": "^2.2.0",
         "next-mdx-remote": "^4.3.0",
         "next-remote-watch": "2.0.0",
-        "postcss": "^8.4.20",
+        "postcss": "^8.4.21",
         "rehype-stringify": "^9.0.3",
         "remark-gfm": "^3.0.1",
         "tailwindcss": "^3.2.4",
@@ -11813,9 +11813,9 @@
       }
     },
     "node_modules/postcss": {
-      "version": "8.4.20",
-      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.20.tgz",
-      "integrity": "sha512-6Q04AXR1212bXr5fh03u8aAwbLxAQNGQ/Q1LNa0VfOI06ZAlhPHtQvE4OIdpj4kLThXilalPnmDSOD65DcHt+g==",
+      "version": "8.4.21",
+      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.21.tgz",
+      "integrity": "sha512-tP7u/Sn/dVxK2NnruI4H9BG+x+Wxz6oeZ1cJ8P6G/PZY0IKk4k/63TDsQf2kQq3+qoJeLm2kIBUNlZe3zgb4Zg==",
       "funding": [
         {
           "type": "opencollective",

web/package.json

@@ -53,7 +53,7 @@
     "netlify-plugin-cypress": "^2.2.0",
     "next-mdx-remote": "^4.3.0",
     "next-remote-watch": "2.0.0",
-    "postcss": "^8.4.20",
+    "postcss": "^8.4.21",
     "rehype-stringify": "^9.0.3",
     "remark-gfm": "^3.0.1",
     "tailwindcss": "^3.2.4",