Update django-anymail from 5.0 to 6.0
@@ -14,4 +14,4 @@ sentry-sdk==0.7.6 # https://github.com/getsentry/sentry-python
# Django
# ------------------------------------------------------------------------------
django-storages[boto3]==1.7.1 # https://github.com/jschneier/django-storages
-django-anymail[mailgun]==5.0 # https://github.com/anymail/django-anymail
+django-anymail[mailgun]==6.0 # https://github.com/anymail/django-anymail
