docs(toh-5): fix typo in link (#2622)

.htm => .html

Author: mauricedb

public/docs/ts/latest/tutorial/toh-pt5.jade

@@ -657,7 +657,7 @@ block extract-id
   What kind of class? 
   The current `RouterModule.forRoot()` produces an Angular `ModuleWithProviders` which suggests that a
   class dedicated to routing should be some kind of module.
-  It should be a [_Routing Module_](../guide/router.htm#routing-module).
+  It should be a [_Routing Module_](../guide/router.html#routing-module).
 
   By convention the name of a _Routing Module_ contains the word "Routing" and 
   aligns with the name of the module that declares the components navigated to".