Bump django-anymail[mailgun] from 8.6 to 11.0

Bumps [django-anymail[mailgun]](https://github.com/anymail/django-anymail) from 8.6 to 11.0.
- [Release notes](https://github.com/anymail/django-anymail/releases)
- [Changelog](https://github.com/anymail/django-anymail/blob/main/CHANGELOG.rst)
- [Commits](anymail/django-anymail@v8.6...v11.0)

---
updated-dependencies:
- dependency-name: django-anymail[mailgun]
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements/base.txt

@@ -1,7 +1,7 @@
 # Django
 django==4.2.14
 django-allauth==0.63.4
-django-anymail[mailgun]==8.6
+django-anymail[mailgun]==11.0
 django-autoslug==1.9.9  # https://github.com/justinmayer/django-autoslug
 django-ckeditor==6.7.1 # Todo: Unused, remove.
 django-cors-headers==3.14.0