Steps to reproduce:
1.Edit the 'Home' landing page
2. Setup publish later for the Home draft Version 2
3. Edit 'Home' again and create a new draft
4. Setup publish later for the Home draft Version 3
5. Edit Version 3 again and select the option to Discard publish later

Error: Publish later is discarded for both Version 2 and Version 3.

Expected behavior: Only publish later for Version 3 should be discarded