Fix django-filter version
Fix django-filter version

As using `*` currently selects 2.3.0 which requires `django >= 2.2`, which is not compatible with the rest of the Pipfile

`ERROR: ERROR: Could not find a version that matches django<1.12,>=1.11,>=1.11.0,>=2.2`
lapo-luchini/pinry,lapo-luchini/pinry,pinry/pinry,lapo-luchini/pinry,lapo-luchini/pinry,pinry/pinry,pinry/pinry,pinry/pinry