Update dependency eslint to v9

Author: renovate[bot]

frontend-demo/package.json

@@ -45,7 +45,7 @@
     "@types/react-dom": "^18.3.0",
     "@typescript-eslint/eslint-plugin": "^8.13.0",
     "@typescript-eslint/typescript-estree": "^8.13.0",
-    "eslint": "^8",
+    "eslint": "^9.0.0",
     "eslint-config-mitodl": "^2.1.0",
     "eslint-config-next": "15.1.6",
     "eslint-config-prettier": "^9.0.0",