Bump django from 3.0 to 3.0.3 in /examples/cookbook (#876)

Bumps [django](https://github.com/django/django) from 3.0 to 3.0.3. - [Release notes](https://github.com/django/django/releases) - [Commits](django/django@3.0...3.0.3) Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

examples/cookbook/requirements.txt

@@ -1,5 +1,5 @@
 graphene>=2.1,<3
 graphene-django>=2.1,<3
 graphql-core>=2.1,<3
-django==3.0
+django==3.0.3
 django-filter>=2