don't include dev sandcastles in prod

Author: jjspace

packages/sandcastle/sandcastle.config.js

@@ -1,3 +1,5 @@
+import process from "process";
+
 const config = {
   root: ".",
   sourceUrl: "https://github.com/CesiumGS/cesium/blob/main/packages/sandcastle",
@@ -19,7 +21,7 @@ const config = {
       labels: [],
       development: false,
     },
-    includeDevelopment: true,
+    includeDevelopment: !process.env.PROD,
   },
 };