Bump django from 2.1.11 to 2.2.13

Bumps [django](https://github.com/django/django) from 2.1.11 to 2.2.13.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@2.1.11...2.2.13)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

requirements.txt

@@ -1,6 +1,6 @@
 colorama==0.4.3
 concept-formation==0.3.4
-Django==2.1.11
+Django==2.2.13
 django-flashpolicies==1.10
 django-extensions==2.2.8
 django-picklefield @ git+https://github.com/eharpste/django-picklefield.git