Ignored pkg_resources deprecation warnings (#1146)

This is to fix failing CI. Should actually be fixed in
django-polymorphic where pkg_resources is used.

Author: sliverc

setup.cfg

@@ -65,6 +65,9 @@ filterwarnings =
     error::PendingDeprecationWarning
     # Remove when DRF is not depending on it anymore
     ignore:The django.utils.timezone.utc alias is deprecated.
+    # can be removed once fixed in django polymorphic
+    ignore:pkg_resources is deprecated as an API
+    ignore:Deprecated call to `pkg_resource
 testpaths =
     example
     tests