Update tornado to 6.2

Remove unneeded imports from jsonschema for synctoken
Update optional requirements
Remove invalid direction arrows in comic reader

cps/services/SyncToken.py

@@ -19,10 +19,8 @@
 
 import sys
 from base64 import b64decode, b64encode
-from jsonschema import validate, exceptions, __version__
-from datetime import datetime, timezone
-
-from urllib.parse import unquote
+from jsonschema import validate, exceptions
+from datetime import datetime
 
 from flask import json
 from .. import logger