Update dependency postcss to v8.4.19

Author: renovate[bot]

frontend/package.json

@@ -52,7 +52,7 @@
     "autoprefixer": "10.4.8",
     "less": "4.1.3",
     "less-loader": "11.0.0",
-    "postcss": "8.4.16",
+    "postcss": "8.4.19",
     "tailwindcss": "3.1.8",
     "typescript": "^4.9.3",
     "vite": "3.0.9",