Fix documentation typo
Fix documentation typo

Thanks to typeshige for the report.

michaelkuty/feincms,mjl/feincms,mjl/feincms,pjdelport/feincms,joshuajonah/feincms,joshuajonah/feincms,michaelkuty/feincms,matthiask/django-content-editor,nickburlett/feincms,pjdelport/feincms,nickburlett/feincms,michaelkuty/feincms,matthiask/django-content-editor,michaelkuty/feincms,matthiask/feincms2-content,feincms/feincms,matthiask/django-content-editor,nickburlett/feincms,feincms/feincms,pjdelport/feincms,joshuajonah/feincms,nickburlett/feincms,matthiask/feincms2-content,matthiask/feincms2-content,matthiask/django-content-editor,joshuajonah/feincms,feincms/feincms,mjl/feincms