fix: testapps/next/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-NEXT-8602067

Author: snyk-bot

Diff for: testapps/next/package.json

@@ -14,7 +14,7 @@
   "dependencies": {
     "@tolgee/format-icu": "6.0.0",
     "@tolgee/react": "6.0.0",
-    "next": "15.1.0",
+    "next": "15.1.2",
     "react": "18.3.1",
     "react-dom": "18.3.1"
   },