[1.5.x] Fixed #20543 - Typo in db model fields docs.
[1.5.x] Fixed #20543 - Typo in db model fields docs.

Thanks i.amber.jain@ for the report.

Backport of f315693304 from master

alx-eu/django,ccn-2m/django,ccn-2m/django,bliti/django-nonrel-1.5,imtapps/django-imt-fork,hasadna/django,ccn-2m/django,ccn-2m/django,hasadna/django,alx-eu/django,imtapps/django-imt-fork,imtapps/django-imt-fork,bliti/django-nonrel-1.5,bliti/django-nonrel-1.5,alx-eu/django,alx-eu/django,hasadna/django