docs: pin Pro next.6 for site builds

Author: olegberman

apps/site/package.json

@@ -13,7 +13,7 @@
     "@astrojs/check": "^0.9.9",
     "@astrojs/react": "^5.0.4",
     "@astrojs/starlight": "^0.39.2",
-    "@chart-kit/pro": "7.0.0-next.4",
+    "@chart-kit/pro": "7.0.0-next.6",
     "astro": "^6.3.1",
     "react": "^19.2.6",
     "react-dom": "^19.2.6",