The ``choices`` field on the ``wagtailforms.models.AbstractFormField`` model has been changed from a ``CharField`` to a ``TextField``, to allow it to be of unlimited length. If you are using the ``wagtailforms`` module in your project, you will need to run ``python manage.py makemigrations`` and ``python manage.py migrate`` after upgrading, in order to apply this change to your form page models.
The ``wagtailimages.Filter`` model has been removed, and replaced with a ``Filter`` class instead. This class can be imported from the same location as the model: ``wagtail.wagtailimages.models.Filter``. The ``Filter`` class has the same API as the ``Filter`` model did, with the exception that Model methods such as ``Filter.save()``, and ``Filter.objects.get()`` have been removed.