build(deps): bump postcss from 8.4.20 to 8.4.21 (#1427)

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:production
  update-type: version-update:semver-patch
...

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

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

package.json

@@ -79,7 +79,7 @@
         "monaco-themes": "^0.4.3",
         "mq-polyfill": "1.1.8",
         "navigator.locks": "^0.8.6",
-        "postcss": "^8.4.20",
+        "postcss": "^8.4.21",
         "postcss-flexbugs-fixes": "^5.0.2",
         "postcss-loader": "^7.0.2",
         "postcss-normalize": "^10.0.1",

yarn.lock

@@ -2491,7 +2491,7 @@ __metadata:
     monaco-themes: ^0.4.3
     mq-polyfill: 1.1.8
     navigator.locks: ^0.8.6
-    postcss: ^8.4.20
+    postcss: ^8.4.21
     postcss-flexbugs-fixes: ^5.0.2
     postcss-loader: ^7.0.2
     postcss-normalize: ^10.0.1
@@ -12569,7 +12569,7 @@ __metadata:
   languageName: node
   linkType: hard
 
-"postcss@npm:^8.2.14, postcss@npm:^8.4.17, postcss@npm:^8.4.18, postcss@npm:^8.4.19, postcss@npm:^8.4.20":
+"postcss@npm:^8.2.14, postcss@npm:^8.4.17, postcss@npm:^8.4.18, postcss@npm:^8.4.19":
   version: 8.4.20
   resolution: "postcss@npm:8.4.20"
   dependencies:
@@ -12580,6 +12580,17 @@ __metadata:
   languageName: node
   linkType: hard
 
+"postcss@npm:^8.4.21":
+  version: 8.4.21
+  resolution: "postcss@npm:8.4.21"
+  dependencies:
+    nanoid: ^3.3.4
+    picocolors: ^1.0.0
+    source-map-js: ^1.0.2
+  checksum: e39ac60ccd1542d4f9d93d894048aac0d686b3bb38e927d8386005718e6793dbbb46930f0a523fe382f1bbd843c6d980aaea791252bf5e176180e5a4336d9679
+  languageName: node
+  linkType: hard
+
 "prelude-ls@npm:^1.2.1":
   version: 1.2.1
   resolution: "prelude-ls@npm:1.2.1"