Added TemplatesSetting to list of built-in renderers in FORM_RENDERER docs.

docs/ref/settings.txt

@@ -1705,6 +1705,7 @@ renderers are:
 
 * ``'``:class:`django.forms.renderers.DjangoTemplates`\ ``'``
 * ``'``:class:`django.forms.renderers.Jinja2`\ ``'``
+* ``'``:class:`django.forms.renderers.TemplatesSetting`\ ``'``
 
 .. setting:: FORMAT_MODULE_PATH