Bump django from 2.1.9 to 2.1.11 in /examples/python-postgres (#87)

Bumps [django](https://github.com/django/django) from 2.1.9 to 2.1.11.
- [Release notes](https://github.com/django/django/releases)
- [Commits](https://github.com/django/django/compare/2.1.9...2.1.11)

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

examples/python-postgres/requirements.txt

@@ -1,4 +1,4 @@
-Django==2.1.9
+Django==2.1.11
 pytz==2019.1
 sqlparse==0.3.0
 psycopg2-binary==2.8.3