Bump django from 2.1.10 to 2.1.11 in /examples/cookbook-plain (#733)

dependabot[bot] · jkimbo · commit 930adb50ce3d · 2019-08-07T08:09:56.000+01:00
Bumps [django](https://github.com/django/django) from 2.1.10 to 2.1.11. - [Release notes](https://github.com/django/django/releases) - [Commits](django/django@2.1.10...2.1.11) Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/examples/cookbook-plain/requirements.txt b/examples/cookbook-plain/requirements.txt
@@ -1,4 +1,4 @@
 graphene
 graphene-django
 graphql-core>=2.1rc1
-django==2.1.10
+django==2.1.11
