docs(toh-pt5): fix typo in tutorial

closes #1913

Author: benoit-lateltin

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

@@ -624,7 +624,7 @@ figure.image-display
     **The *routerLinkActive* directive**
 
     The Angular Router provides a `routerLinkActive` directive we can use to
-    to add a class to the HTML navigation element whose route matches the active route.
+    add a class to the HTML navigation element whose route matches the active route.
     All we have to do is define the style for it. Sweet!
 +makeExample('toh-5/ts/app/app.component.3.ts', 'router-link-active', 'app/app.component.ts (active router links)')(format=".")
 :marked