Fix `el.id` not being defined in DjangoPagedown.destroyEditor
Fix `el.id` not being defined in DjangoPagedown.destroyEditor

This seems like a regression from 9ffcbb7, as all instances of `el`
was replaced by `element`. However, this instance was missed.

timmyomahony/django-pagedown,timmyomahony/django-pagedown,timmyomahony/django-pagedown