If you want to remove the old repository you’ll need to do so manually. This command will provide you with the file name that contains the old URL. From there, you can use vi or nano to remove it. There is no need to remove it, but will aide in cleaner command line output and logs:
If your repository is located outside of /etc/apt for some reason, you'll need to locate the file manually.
Of course, after you run the above commands, you'll need to:
sudo apt-get update && sudo apt-get upgrade
We will link to these instructions within release announcements for the next few releases, but the instructions included in future release announcements will assume that you have the repository in your apt lists already.