docs(toh): remove duplicate "the" (#3321)

Author: MichaelFoss

public/docs/ts/latest/tutorial/toh-pt6.jade

@@ -416,7 +416,7 @@ block observables-section-intro
 +ifDocsFor('ts')
   :marked
     A more important difference: we no longer call `toPromise`.
-    Instead we return the *observable* from the the `http.get`, 
+    Instead we return the *observable* from the `http.get`, 
     after chaining it to another RxJS operator, <code>map</code>, 
     to extract heroes from the response data.