Delete shared notes on iCloud.com
In Notes on iCloud.com, select the shared note that you want to delete.
If you do not see the notes list, see Show the folder or notes list in Notes on iCloud.com.
Tap the Delete button in the Toolbar, then tap OK.
One of the following happens:
If you are the owner: the note is removed from the devices of everyone you shared it with. You can recover your recently deleted notes from your Recently Deleted folder.
If you are a participant: the note is removed from your notes list, but not from the owner’s notes list or any other participant’s notes list. The note does not move to your Recently Deleted folder. You can open and edit the note again by tapping the original link that the owner shared, unless the owner stopped sharing the note.