Update dependency autoprefixer to v10.4.21

Author: renovate[bot]

package-lock.json

@@ -17,7 +17,7 @@
     "reconnecting-websocket": "4.4.0"
   },
   "devDependencies": {
-    "autoprefixer": "10.4.20",
+    "autoprefixer": "10.4.21",
     "copy-webpack-plugin": "12.0.2",
     "css-loader": "7.1.2",
     "html-webpack-plugin": "5.6.3",