Removed a redundant colon in the query docs.

    There's one exception though, in case of a

    :class:`~django.db.models.ForeignKey` you can specify the field

    name suffixed with ``_id``. In this case, the value parameter is expected

    to contain the raw value of the foreign model's primary key. For example::

    to contain the raw value of the foreign model's primary key. For example:

        >>> Entry.objects.filter(blog_id__exact=4)