Update setup.py to use django-filter latest version
Update setup.py to use django-filter latest version

The django-filter package has changed its versioning from a semver to a year based one. The latest version (21.1) is the same as the old one that wagtail supported (2.4): https://github.com/carltongibson/django-filter/blob/main/CHANGES.rst 

So we could just bumb the requirement to `<=22` (I think it's fine to use that because the readme claims that breaking changes will be introduced to version+2 so breaking versions for v.21 will be introduced to v.23)
wagtail/wagtail,jnns/wagtail,mixxorz/wagtail,zerolab/wagtail,thenewguy/wagtail,thenewguy/wagtail,rsalmaso/wagtail,wagtail/wagtail,thenewguy/wagtail,rsalmaso/wagtail,jnns/wagtail,zerolab/wagtail,mixxorz/wagtail,wagtail/wagtail,wagtail/wagtail,mixxorz/wagtail,mixxorz/wagtail,rsalmaso/wagtail,mixxorz/wagtail,jnns/wagtail,wagtail/wagtail,jnns/wagtail,rsalmaso/wagtail,thenewguy/wagtail,zerolab/wagtail,thenewguy/wagtail,rsalmaso/wagtail,zerolab/wagtail,zerolab/wagtail