Fixed renamed method in documentation.
Fixed renamed method in documentation.

albedoweb/django-treebeard,torchbox/django-treebeard,velfimov/django-treebeard,velfimov/django-treebeard,torchbox/django-treebeard,velfimov/django-treebeard,kazmiruk/django-treebeard,torchbox/django-treebeard,kazmiruk/django-treebeard,albedoweb/django-treebeard,albedoweb/django-treebeard,kazmiruk/django-treebeard,velfimov/django-treebeard,kazmiruk/django-treebeard,albedoweb/django-treebeard