Bump djangorestframework in /{{cookiecutter.project_slug}} (#306)

Bumps [djangorestframework](https://github.com/encode/django-rest-framework) from 3.12.4 to 3.13.1.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](encode/django-rest-framework@3.12.4...3.13.1)

---
updated-dependencies:
- dependency-name: djangorestframework
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

{{cookiecutter.project_slug}}/Pipfile

@@ -17,7 +17,7 @@ django-storages = "~=1.12"
 psycopg2 = "<2.9"
 waitress = "~=2.0.0"
 whitenoise = "~=5.3.0"
-djangorestframework = "~=3.12.4"
+djangorestframework = "~=3.13.1"
 django-bootstrap4 = "~=21.1"
 django-allauth = "~=0.47.0"
 django-rest-auth = "~=0.9.5"