Fix CSS

I dunno what I was seeing that made me think the width should be 237, but it was incorrect.

src/views/preview/preview.scss

@@ -43,7 +43,7 @@ $stage-width: 480px;
 
     .project-admin-panel.admin-panel-open {
         padding: 0;
-        width: 237px;
+        width: 250px;
     }
 
     .admin-iframe {
@@ -53,7 +53,7 @@ $stage-width: 480px;
         z-index: 100;
         margin: 0;
         border: 0;
-        width: 237px;
+        width: 250px;
         height: 100%;
     }