[mondrian] Increase delay.

Test: manual

Change-Id: I96047584f95dd4073397b13466c5034e162fdacd
diff --git a/shell/mondrian_story_shell/lib/widgets/surface_stage.dart b/shell/mondrian_story_shell/lib/widgets/surface_stage.dart
index e203508..46c4f71 100644
--- a/shell/mondrian_story_shell/lib/widgets/surface_stage.dart
+++ b/shell/mondrian_story_shell/lib/widgets/surface_stage.dart
@@ -30,7 +30,7 @@
 
 /// Delays the first animation by this amount.  This gives new mods time to
 /// load.
-const _introAnimationDelay = Duration(milliseconds: 750);
+const _introAnimationDelay = Duration(milliseconds: 3000);
 
 /// Stages determine how things move, and how they can be manipulated
 class SurfaceStage extends StatelessWidget {