Bump django-appconf from 1.0.2 to 1.0.4 in /cvat/requirements (#1718)

Bumps [django-appconf](https://github.com/django-compressor/django-appconf) from 1.0.2 to 1.0.4.
- [Release notes](https://github.com/django-compressor/django-appconf/releases)
- [Changelog](https://github.com/django-compressor/django-appconf/blob/develop/docs/changelog.rst)
- [Commits](https://github.com/django-compressor/django-appconf/compare/v1.0.2...v1.0.4)

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Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

cvat/requirements/base.txt

@@ -1,6 +1,6 @@
 click==6.7
 Django==2.2.13
-django-appconf==1.0.2
+django-appconf==1.0.4
 django-auth-ldap==1.4.0
 django-cacheops==5.0
 django-compressor==2.2