Merge pull request #5128 from gianlucalimbi/fix-collections-duplicates

[5.8] Fix Collections duplicates docs

Author: taylorotwell

collections.md

@@ -500,17 +500,17 @@ The `dump` method dumps the collection's items:
 
 If you want to stop executing the script after dumping the collection, use the [`dd`](#method-dd) method instead.
 
-<a name="method-duplicates"><a>
+<a name="method-duplicates"></a>
 #### `duplicates()` {#collection-method}
 
 the `duplicates` method retrieves and returns duplicate values from the collection:
 
     $collection = collect(['a', 'b', 'a', 'c', 'b']);
-    
+
     $collection->duplicates();
-    
+
     // [ 2 => 'a', 4 => 'b' ]
-    
+
 <a name="method-each"></a>
 #### `each()` {#collection-method}