fix: docs/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-NEXT-15104645

Author: snyk-bot

docs/package.json

@@ -14,10 +14,10 @@
   "license": "MPL-2.0",
   "dependencies": {
     "@heroicons/react": "~1.0.6",
-    "next": "~12.2.5",
+    "next": "~15.5.10",
     "next-themes": "0.2.0",
     "nextra": "2.0.0-alpha.56",
-    "nextra-theme-docs": "2.2.18",
+    "nextra-theme-docs": "2.0.0",
     "react": "~18.2.0",
     "react-dom": "~18.2.0",
     "swr": "1.3.0"