⚡️ Always return an empty server_to_phone response

We don't actually use the server_to_phone response on the phone since we always
retrieve data from the server. This comments out the data that is returned from
the server so that we don't waste time reading data that we don't use.

We still get the calls as a coarse ping to know that the app is installed and is
working correctly, even if the user is not contributing data. But we don't burn
up bandwidth reading unused data from the server.

This cleanup is part of removing the NEW_DATA implicit intent
e-mission/e-mission-docs#1079 (comment)

emission/net/api/cfc_webapp.py

@@ -235,7 +235,8 @@ def getFromCache():
   logging.debug("Called userCache.get")
   user_uuid=getUUID(request)
   logging.debug("user_uuid %s" % user_uuid)
-  to_phone = usercache.sync_server_to_phone(user_uuid)
+  # to_phone = usercache.sync_server_to_phone(user_uuid)
+  to_phone = []
   return {'server_to_phone': to_phone}
 
 @post('/usercache/put')