Don't override LOGIN_URL and LOGIN_REDIRECT_URL in local settings.

This is a fix for
https://aptivate.kanbantool.com/boards/5986-econsensus#tasks-1385283
but the value for LOGIN_REDIRECT_URL now used is the one suggested by
https://aptivate.kanbantool.com/boards/5986-econsensus#tasks-1251883