CMS-45730 Update next dependency to version 15.5.7 in package.json and pnpm-lock.yaml

Author: TRomesh

pnpm-lock.yaml

@@ -10,7 +10,7 @@
   "dependencies": {
     "@optimizely/cms-sdk": "workspace:*",
     "clsx": "^2.1.1",
-    "next": "15.5.4",
+    "next": "15.5.7",
     "react": "19.1.0",
     "react-dom": "19.1.0",
     "tailwind-merge": "^3.3.1"