Set yarn to 4.9.2

Author: TarikGul

package.json

@@ -6,7 +6,7 @@
   },
   "homepage": "https://github.com/polkadot-js/extension#readme",
   "license": "Apache-2.0",
-  "packageManager": "yarn@4.6.0",
+  "packageManager": "yarn@4.9.2",
   "private": true,
   "repository": {
     "type": "git",