docs(error/ngRepeat/dupes): fix typo

Closes angular#5610

Author: drewp

docs/content/error/ngRepeat/dupes.ngdoc

@@ -13,7 +13,7 @@ For example the issue can be triggered by this *invalid* code:
 <div ng-repeat="value in [4, 4]"></div>
 ```
 
-To resolve this error either ensure that the items in the collection have unique identity of use the `track by` syntax to specify how to track the association between models and DOM.
+To resolve this error either ensure that the items in the collection have unique identity or use the `track by` syntax to specify how to track the association between models and DOM.
 
 To resolve the example above can be resolved by using `track by $index`, which will cause the items to be keyed by their position in the array instead of their value: