Merge pull request #12351 from CesiumGS/update-sandcastle-name

Rename iModel sandcastle

Author: jjspace

Apps/Sandcastle/gallery/iTwin Demo.html renamed to Apps/Sandcastle/gallery/iModel Mesh Export Service.html

@@ -12,7 +12,7 @@
       content="Demonstrate loading iModel data from the iTwin platform."
     />
     <meta name="cesium-sandcastle-labels" content="Showcases, 3D Tiles" />
-    <title>iTwin iModel demo</title>
+    <title>iModel Mesh Export Service</title>
     <script type="text/javascript" src="../Sandcastle-header.js"></script>
     <script type="module" src="../load-cesium-es6.js"></script>
   </head>