fix(deps): update dependency mdast-util-to-string to v4

Author: renovate[bot]

package.json

@@ -20,7 +20,7 @@
     "@fontsource/lexend": "4.5.15",
     "@tailwindcss/typography": "0.5.9",
     "astro": "2.10.4",
-    "mdast-util-to-string": "3.2.0",
+    "mdast-util-to-string": "4.0.0",
     "react": "18.2.0",
     "react-dom": "18.2.0",
     "reading-time": "1.5.0",