Bump postcss from 8.4.19 to 8.4.31 in /assets

Bumps [postcss](https://github.com/postcss/postcss) from 8.4.19 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/8.4.19...8.4.31)

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

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

assets/package-lock.json

@@ -3712,12 +3712,6 @@
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       "dev": true
     },
-    "nanoid": {
-      "version": "3.3.4",
-      "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.3.4.tgz",
-      "integrity": "sha512-MqBkQh/OHTS2egovRtLk45wEyNXwF+cokD+1YPf9u5VfJiRdAiRwB2froX5Co9Rh20xs4siNPm8naNotSD6RBw==",
-      "dev": true
-    },
     "negotiator": {
       "version": "0.6.3",
       "resolved": "https://registry.npmjs.org/negotiator/-/negotiator-0.6.3.tgz",
@@ -4134,19 +4128,6 @@
         "cssnano": "^5.0.2",
         "last-call-webpack-plugin": "^3.0.0",
         "postcss": "^8.2.1"
-      },
-      "dependencies": {
-        "postcss": {
-          "version": "8.4.19",
-          "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.19.tgz",
-          "integrity": "sha512-h+pbPsyhlYj6N2ozBmHhHrs9DzGmbaarbLvWipMRO7RLS+v4onj26MPFXA5OBYFxyqYhUJK456SwDcY9H2/zsA==",
-          "dev": true,
-          "requires": {
-            "nanoid": "^3.3.4",
-            "picocolors": "^1.0.0",
-            "source-map-js": "^1.0.2"
-          }
-        }
       }
     },
     "p-limit": {
@@ -4253,14 +4234,22 @@
       }
     },
     "postcss": {
-      "version": "8.4.20",
-      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.20.tgz",
-      "integrity": "sha512-6Q04AXR1212bXr5fh03u8aAwbLxAQNGQ/Q1LNa0VfOI06ZAlhPHtQvE4OIdpj4kLThXilalPnmDSOD65DcHt+g==",
+      "version": "8.4.31",
+      "resolved": "https://registry.npmjs.org/postcss/-/postcss-8.4.31.tgz",
+      "integrity": "sha512-PS08Iboia9mts/2ygV3eLpY5ghnUcfLV/EXTOW1E2qYxJKGGBUtNjN76FYHnMs36RmARn41bC0AZmn+rR0OVpQ==",
       "dev": true,
       "requires": {
-        "nanoid": "^3.3.4",
+        "nanoid": "^3.3.6",
         "picocolors": "^1.0.0",
         "source-map-js": "^1.0.2"
+      },
+      "dependencies": {
+        "nanoid": {
+          "version": "3.3.6",
+          "resolved": "https://registry.npmjs.org/nanoid/-/nanoid-3.3.6.tgz",
+          "integrity": "sha512-BGcqMMJuToF7i1rt+2PWSNVnWIkGCU78jBG3RxO/bZlnZPK2Cmi2QaffxGO/2RvWi9sL+FAiRiXMgsyxQ1DIDA==",
+          "dev": true
+        }
       }
     },
     "postcss-calc": {