Bump django-anymail from 6.0.1 to 7.0.0

Bumps [django-anymail](https://github.com/anymail/django-anymail) from 6.0.1 to 7.0.0.
- [Release notes](https://github.com/anymail/django-anymail/releases)
- [Changelog](https://github.com/anymail/django-anymail/blob/master/CHANGELOG.rst)
- [Commits](https://github.com/anymail/django-anymail/compare/v6.0.1...v7.0

)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

requirements.txt

@@ -6,7 +6,7 @@ sentry-sdk==0.14.1
 boto3==1.9.245
 celery==4.4.0
 dj-database-url==0.5.0
-django-anymail==6.0.1
+django-anymail==7.0.0
 django-basic-auth-ip-whitelist==0.3.1
 django-bleach==0.6.1
 django-countries==5.5