chore(deps): bump django-maintenance-mode from 0.18.0 to 0.21.1

Bumps [django-maintenance-mode](https://github.com/fabiocaccamo/django-maintenance-mode) from 0.18.0 to 0.21.1.
- [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@0.18.0...0.21.1)

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

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

Pipfile

@@ -17,7 +17,7 @@ defusedxml = "==0.7.1"
 django-appconf = "==1.0.5"
 django-bootstrap3 = "==23.4"
 django-debug-toolbar = "==4.2.0"
-django-maintenance-mode = "==0.18.0"
+django-maintenance-mode = "==0.21.1"
 html5lib = "==1.1"
 httplib2 = "==0.22.0"
 idna = "==3.4"