Merge pull request google#604 from talkor/patch-1

Remove duplicated header

Author: grant

docs/promises.md

@@ -224,9 +224,6 @@ personFetcher.fetch('John');
 
 ## Migrating from callbacks to promises
 
-Migrating from callbacks to promises
-------------------------------------
-
 The `result` parameter of the fulfilled promise value is equivalent to the first parameter in [`execute`](/api-client-library/javascript/reference/referencedocs#gapiclientRequestexecute)'s callback. To update your code to use promises, change your code as shown in the before and after examples below.
 
 The following example shows using a callback:
@@ -249,4 +246,4 @@ gapi.client.request({
  }).then(function(resp) {
    processResponse(resp.result);
  });
-```
+```