docs(cookbook): fix spelling error for word 'class' (angular#2682)

Author: wKoza

public/docs/ts/latest/cookbook/component-communication.jade

@@ -246,7 +246,7 @@ a(id="countdown-tests")
   Here is the parent, `CountdownViewChildParentComponent`:
 +makeExample('cb-component-communication/ts/app/countdown-parent.component.ts', 'vc')
 :marked
-  It takes a bit more work to get the child view into the parent component classs.
+  It takes a bit more work to get the child view into the parent component *class*.
 
   We import references to the `ViewChild` decorator and the `AfterViewInit` lifecycle hook.