Bump django from 3.0.3 to 3.0.7 in /examples/cookbook (#979)

Bumps [django](https://github.com/django/django) from 3.0.3 to 3.0.7.
- [Release notes](https://github.com/django/django/releases)
- [Commits](django/django@3.0.3...3.0.7)

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.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==3.0.3
+django==3.0.7
 django-filter>=2