chore(deps): update devdependency eslint to v9.21.0

Author: renovate[bot]

package.json

@@ -66,7 +66,7 @@
     "@vitest/coverage-v8": "2.1.9",
     "acorn": "8.14.0",
     "bumpp": "10.0.3",
-    "eslint": "9.20.1",
+    "eslint": "9.21.0",
     "expect-type": "1.1.0",
     "lint-staged": "latest",
     "rollup": "4.34.8",