Bump djangorestframework from 3.14.0 to 3.15.2

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] <[email protected]>

requirements.txt

@@ -7,7 +7,7 @@ django-json-rpc==0.7.2
 django-location-field==2.1.0
 django-recaptcha==3.0.0
 django-reservation==0.2.10
-djangorestframework==3.14.0
+djangorestframework==3.15.2
 openpyxl==3.0.3
 Pillow>=7.1.2
 psycopg2-binary==2.9.5