Update router.jade (#3265)

Author: DeborahK

public/docs/ts/latest/guide/router.jade

@@ -2576,7 +2576,7 @@ a#custom-preloading
   Shortly, you'll extend the `AdminDashboardComponent` to inject this service and display its `preloadedModules` array.
 
   But first, make a few changes to the `AppRoutingModule`.
-  1. Import `SelectivePreloadingStrategy` into .
+  1. Import `SelectivePreloadingStrategy` into `AppRoutingModule`.
   1. Replace the `PreloadAllModules` strategy in the call to `forRoot` with this `SelectivePreloadingStrategy`. 
   1. Add the `SelectivePreloadingStrategy` strategy to the `AppRoutingModule` providers array so it can be injected 
   elsewhere in the app.