Group folder notification not showing the last editor of a document

The notification of changes to a document in the group folder does not show the last editor of the document if versioning is disabled.

How to reproduce:

• Disable versioning on the system
• User A: In a group open the folder tool and subscribe
• Upload a .docx file
• Result: Under subscriptions the notification overview displays "File ... altered by User A"
• User B: Open the same group in another browser window
• Open the folder tool
• Open the document uploaded by User A with the OnlyOffice Online Editor, edit and close it
• Maybe wait a little bit until the lock symbol at the file is gone again
• NOK: Under subscriptions the notification shows "File ... altered by User A"
• OK: In the subscriptions, both users will see "File ... altered by User B" (as with activated versioning)

For now we change the message in the notifications. In the future we will store the last modifier in the metadatas as well (OO-5093).