fix: requirements.txt to reduce vulnerabilities

The following vulnerabilities are fixed by pinning transitive dependencies:
- https://snyk.io/vuln/SNYK-PYTHON-EVENTLET-8136230

requirements.txt

@@ -13,7 +13,7 @@ pymysql==1.1.0
 pyjwt==2.8.0
 coverage==7.3.0
 https://github.com/benoitc/gunicorn/archive/refs/heads/master.zip#egg=gunicorn==20.1.0 # eventlet bug workaround
-eventlet==0.33.3
+eventlet==0.37.0
 flask-wtf==1.1.1
 flask-login==0.6.2
 flask-redmail==0.3.0