Bump djangorestframework from 3.14.0 to 3.15.2 in /requirements

Bumps [djangorestframework](https://github.com/encode/django-rest-framework) from 3.14.0 to 3.15.2.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](encode/django-rest-framework@3.14.0...3.15.2)

---
updated-dependencies:
- dependency-name: djangorestframework
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements/base.txt

@@ -8,7 +8,7 @@ django-model-utils==4.3.1
 Markdown==3.5.1
 django-localflavor==4.0
 django-extensions==3.2.3
-djangorestframework==3.14.0
+djangorestframework==3.15.2
 django-redis==5.3.0
 hiredis==2.3.2
 redis==5.0.4