Update dependency chai to v6

Author: renovate[bot]

package.json

@@ -26,7 +26,7 @@
     "hexo-util": "1.9.0"
   },
   "devDependencies": {
-    "chai": "4.2.0",
+    "chai": "6.2.0",
     "eslint": "6.8.0",
     "eslint-config-theme-next": "1.1.4",
     "hexo": "4.2.0",