Bump pytest-django from 3.8.0 to 3.9.0

Bumps [pytest-django](https://github.com/pytest-dev/pytest-django) from 3.8.0 to 3.9.0.
- [Release notes](https://github.com/pytest-dev/pytest-django/releases)
- [Changelog](https://github.com/pytest-dev/pytest-django/blob/master/docs/changelog.rst)
- [Commits](pytest-dev/pytest-django@v3.8.0...v3.9.0)

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

requirements/local.txt

@@ -15,7 +15,7 @@ requests==2.22.0
 iiif-prezi==0.3.0 # https://github.com/iiif-prezi/iiif-prezi
 httpretty==1.0.2 # https://pypi.org/project/httpretty/
 cssutils==1.0.2 # https://pypi.org/project/cssutils/
-pytest-django==3.8.0  # https://github.com/pytest-dev/pytest-django
+pytest-django==3.9.0  # https://github.com/pytest-dev/pytest-django
 
 # Code quality
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