Bump django from 3.1.5 to 3.1.7

Bumps [django](https://github.com/django/django) from 3.1.5 to 3.1.7.
- [Release notes](https://github.com/django/django/releases)
- [Commits](https://github.com/django/django/compare/3.1.5...3.1.7)

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

requirements.txt

@@ -1,5 +1,5 @@
 asgiref==3.3.1
-Django==3.1.5
+Django==3.1.7
 pytz==2020.5
 sqlparse==0.4.1
 requests