Revert "use latest version of redis and flask"

This reverts commit 322aad05.

requirements.txt

 bcrypt==3.1.7
 ffmpy==0.2.2
-Flask
-Flask-Caching
-Flask-Session
-Flask-WTF
+Flask==1.1.1
+Flask-Caching==1.8.0
+Flask-Session==0.3.1
+Flask-WTF==0.14.3
 gunicorn==20.0.4
 jsonschema==3.2.0
 pymongo==3.10.1
-redis
+redis==3.4.1
 requests==2.23.0
 websockets==7.0