Bump django from 2.2.10 to 2.2.13

Bumps [django](https://github.com/django/django) from 2.2.10 to 2.2.13.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@2.2.10...2.2.13)

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

Author: dependabot[bot]

requirements.txt

@@ -1,4 +1,4 @@
-Django==2.2.10
+Django==2.2.13
 djangorestframework==3.10.3
 pytz==2019.2
 sqlparse==0.3.0