Bump djangorestframework from 3.11.0 to 3.15.2

Bumps [djangorestframework](https://github.com/encode/django-rest-framework) from 3.11.0 to 3.15.2.
- [Release notes](https://github.com/encode/django-rest-framework/releases)
- [Commits](encode/django-rest-framework@3.11.0...3.15.2)

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

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -9,7 +9,7 @@ Django==2.2.9
 django-after-response==0.2.2
 django-bootstrap4==22.1
 django-health-check==3.12.1
-djangorestframework==3.13.1
+djangorestframework==3.15.2
 emoji-data-python==1.5.0
 gunicorn==22.0.0
 git+https://github.com/hmcts/[email protected]#egg=response