Scheduled publication requests are not cleared when document is published immediately

When a document is scheduled for publication and is then published immediately, the scheduled publication request is not cleared automatically.

Steps to reproduce:
1. create a new document
2. schedule the document for publication
3. publish the document immediately

Expected behavior: the scheduled publication request is canceled automatically
Actual behavior: the scheduled publication request remains, and can only be canceled manually

The same goes for scheduling for unpublication. Steps to reproduce:
1. create a new document
2. publish the document
3. schedule the document for unpublication
3. unpublish the document immediately

Expected behavior: the scheduled unpublication request is canceled automatically
Actual behavior: the scheduled unpublication request remains, and can only be canceled manually