Update django-environ requirement from <0.9,>=0.4 to >=0.4,<0.10

Updates the requirements on [django-environ](https://github.com/joke2k/django-environ) to permit the latest version.
- [Release notes](https://github.com/joke2k/django-environ/releases)
- [Changelog](https://github.com/joke2k/django-environ/blob/main/CHANGELOG.rst)
- [Commits](https://github.com/joke2k/django-environ/compare/v0.4...v0.9.0)

---
updated-dependencies:
- dependency-name: django-environ
  dependency-type: direct:production
...

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

requirements.txt

@@ -8,7 +8,7 @@ psycopg2-binary>=2.8,<2.10
 
 # Sandbox
 Whoosh>=2.7,<2.8
-django-environ>=0.4,<0.9
+django-environ>=0.4,<0.10
 django-redis>=4.12,<5.3
 pysolr>=3.9,<3.10
 redis>=3.5,<4.4