docs(structural-directives): small grammar fixes in documentation (#3332)

Author: nhnb

public/docs/ts/latest/guide/structural-directives.jade

@@ -364,7 +364,7 @@ a#one-per-element
 :marked
   ### One structural directive per host element
 
-  Someday you'll want to to repeat a block of HTML but only when a particular condition is true.
+  Someday you'll want to repeat a block of HTML but only when a particular condition is true.
   You'll _try_ to put both an `*ngFor` and an `*ngIf` on the same host element.
   Angular won't let you. You may apply only one _structural_ directive to an element. 
 
@@ -467,9 +467,9 @@ block unless-intro
 
     * Import the `Directive` decorator (instead of the `Component` decorator).
 
-    * Import the `Input`, `TemplateRef`, and `ViewContainerRef` symbols; you'll them need for _any_ structural directive.
+    * Import the `Input`, `TemplateRef`, and `ViewContainerRef` symbols; you'll need them for _any_ structural directive.
 
-    * Apply the decorator to to the directive class.
+    * Apply the decorator to the directive class.
 
     * Set the CSS *attribute selector* that identifies the directive when applied to an element in a template.