[deps] Update djangorestframework requirement from <3.15.2,>=3.14 to >=3.14,<3.16.1

Updates the requirements on [djangorestframework](https://github.com/encode/django-rest-framework) to permit the latest version.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](encode/django-rest-framework@3.14.0...3.16.0)

updated-dependencies:
- dependency-name: djangorestframework
  dependency-version: 3.16.0
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Federico Capoano <f.capoano@openwisp.io>

Author: dependabot[bot]

Diff for: setup.py

@@ -42,7 +42,7 @@
             'docstrfmt~=1.8.0',
         ],
         'rest': [
-            'djangorestframework>=3.14,<3.15.2',
+            'djangorestframework>=3.14,<3.17',
             'django-filter~=23.2',  # django-filter uses CalVer
             'drf-yasg~=1.21.7',
         ],