fix: docs/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-NEXT-10259370

Author: snyk-bot

docs/package.json

@@ -83,7 +83,7 @@
     "lz-string": "^1.5.0",
     "markdown-to-jsx": "^7.4.7",
     "material-ui-popup-state": "^5.1.2",
-    "next": "^14.2.5",
+    "next": "^15.2.2",
     "notistack": "3.0.1",
     "nprogress": "^0.2.0",
     "postcss": "^8.4.41",