use extensions in embedded viewer to not break compat

src/apps/viewer/embedded.html

@@ -21,8 +21,6 @@
         <script type="text/javascript" src="./molstar.js"></script>
         <script type="text/javascript">
             var viewer = new molstar.Viewer('app', {
-                extensions: [],
-
                 layoutIsExpanded: false,
                 layoutShowControls: false,
                 layoutShowRemoteState: false,