Bump django from 2.1.6 to 2.2.13 in /examples/server/wsgi/django_example

Bumps [django](https://github.com/django/django) from 2.1.6 to 2.2.13.
- [Release notes](https://github.com/django/django/releases)
- [Commits](https://github.com/django/django/compare/2.1.6...2.2.13)

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

examples/server/wsgi/django_example/requirements.txt

@@ -1,4 +1,4 @@
-django==2.1.6
+django==2.2.13
 enum-compat==0.0.2
 eventlet==0.21.0
 greenlet==0.4.12