chore(internal): upgrade eslint

Author: stainless-app[bot]

package.json

@@ -35,7 +35,7 @@
     "@types/node": "^20.17.6",
     "@typescript-eslint/eslint-plugin": "8.31.1",
     "@typescript-eslint/parser": "8.31.1",
-    "eslint": "^9.20.1",
+    "eslint": "^9.39.1",
     "eslint-plugin-prettier": "^5.4.1",
     "eslint-plugin-unused-imports": "^4.1.4",
     "iconv-lite": "^0.6.3",