fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-DJANGORESTFRAMEWORK-7252137

Author: snyk-bot

requirements.txt

@@ -25,7 +25,7 @@ django-filter==2.4.0
 django-fontawesome-5==1.0.18
 django-getenv==1.3.2
 django-widget-tweaks==1.4.8
-djangorestframework==3.12.4
+djangorestframework==3.15.2
 drf-yasg==1.20.0
 executing==2.0.1
 fonttools==4.49.0