Update Yarn to v4.9.4

Author: renovate[bot]

package.json

@@ -6,7 +6,7 @@
     "name": "mlc"
   },
   "repository": "github:mlc/tpg-solver",
-  "packageManager": "[email protected].2",
+  "packageManager": "[email protected].4",
   "scripts": {
     "build": "node build.mjs",
     "serve": "node build.mjs serve",