Bump django-maintenance-mode from 0.15.1 to 0.20.0 (#393)

Bumps [django-maintenance-mode](https://github.com/fabiocaccamo/django-maintenance-mode) from 0.15.1 to 0.20.0.
- [Release notes](https://github.com/fabiocaccamo/django-maintenance-mode/releases)
- [Changelog](https://github.com/fabiocaccamo/django-maintenance-mode/blob/main/CHANGELOG.md)
- [Commits](fabiocaccamo/django-maintenance-mode@0.15.1...0.20.0)

---
updated-dependencies:
- dependency-name: django-maintenance-mode
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements.txt

@@ -6,7 +6,7 @@ django-debug-toolbar==3.2.1
 django-storages==1.12.3
 djangorestframework==3.13.1
 django-filter==2.4.0
-django-maintenance-mode==0.15.1
+django-maintenance-mode==0.20.0
 django-pipeline==2.0.6
 django-cors-headers==3.7.0
 celery[redis]==5.3.6