remove unused benchmark directory

Author: jeroenvervaeke

benchmark/bench.ts

@@ -43,7 +43,6 @@
   },
   "scripts": {
     "artifacts": "napi artifacts",
-    "bench": "node --import @oxc-node/core/register benchmark/bench.ts",
     "build": "napi build --platform --release --no-const-enum",
     "build:debug": "napi build --platform --no-const-enum",
     "format": "run-p format:prettier format:rs format:toml",