Update dependency next to v15.4.8 [SECURITY]

Author: renovate[bot]

package.json

@@ -13,7 +13,7 @@
     "fathom-client": "3.5.0",
     "front-matter": "4.0.2",
     "lodash": "4.17.21",
-    "next": "15.0.5",
+    "next": "15.4.8",
     "next-mdx-remote": "5.0.0",
     "prismjs": "1.29.0",
     "react": "18.3.1",