fix: upgrade posthog-js from 1.223.5 to 1.266.3

Snyk has created this PR to upgrade posthog-js from 1.223.5 to 1.266.3.

See this package in npm:
posthog-js

See this project in Snyk:
https://app.snyk.io/org/authzed/project/ba1f5e2c-3779-4576-a375-1b68f7cd2dae?utm_source=github&utm_medium=referral&page=upgrade-pr

Author: snyk-bot

package.json

@@ -32,7 +32,7 @@
     "next-sitemap": "^4.2.3",
     "nextra": "^2.13.4",
     "nextra-theme-docs": "^2.13.4",
-    "posthog-js": "^1.223.5",
+    "posthog-js": "^1.266.3",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
     "react-youtube": "^10.1.0",