[1.8.x] Fixed typo in SelectDateWidget docs.
[1.8.x] Fixed typo in SelectDateWidget docs.

Backport of f46f1737aa456c1dc377e3f1f4d307d52d8598af from master

h4r5h1t/django-hauthy,h4r5h1t/django-hauthy,h4r5h1t/django-hauthy,h4r5h1t/django-hauthy