Update dependency eslint to v9

Author: renovate[bot]

package.json

@@ -26,7 +26,7 @@
     "next-util": "^1.0.0"
   },
   "devDependencies": {
-    "eslint": "6.8.0",
+    "eslint": "9.39.2",
     "eslint-config-theme-next": "1.1.4"
   }
 }