Fixed typo in docs/ref/models/fields.txt.
@@ -626,7 +626,7 @@ A :class:`CharField` that checks that the value is a valid email address using
A file-upload field.
.. note::
- The ``primary_key`` argument isn't supported and will raise a an error if
+ The ``primary_key`` argument isn't supported and will raise an error if
used.
Has two optional arguments:
