fix: backend_app/requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-10390193
- https://snyk.io/vuln/SNYK-PYTHON-URLLIB3-10390194

Author: snyk-bot

backend_app/requirements.txt

@@ -67,7 +67,7 @@ supervisor==4.1.0
 tqdm==4.56.0
 typing-extensions==3.7.4.3
 uritemplate==3.0.1
-urllib3==1.26.5
+urllib3==2.5.0
 vine==1.3.0
 yarl==1.4.2
 zipp==0.6.0