Add missing parenthesis to example (#597)

Author: guilleijo

AUTHORS.rst

@@ -38,6 +38,7 @@ Authors
 - George Vilches
 - Gregory Bataille
 - Grzegorz Bialy
+- Guillermo Eijo (`guilleijo <https://github.com/guilleijo>`_)
 - Hamish Downer
 - Hanyin Zhang
 - James Muranga (`jamesmura <https://github.com/jamesmura>`_)

docs/historical_model.rst

@@ -253,7 +253,7 @@ source model. This is possible by combining the ``bases`` functionality with the
         question = models.CharField(max_length=200)
         pub_date = models.DateTimeField('date published')
 
-        history = HistoricalRecords(bases=[IPAddressHistoricalModel,]
+        history = HistoricalRecords(bases=[IPAddressHistoricalModel,])
 
 
 .. code-block:: python