Client anounces folder removal, but does not remove.

[jnweiger]

I decide to sync one of my local folders with an owncloud server.
One subfolder called trebuchet is so huge, that I don't want to upload it now, but perhaps later.

Using selective sync, I can disable that folder, but then a message appears, that says, the folder would be deleted. A cautious user would now copy the huge folder away, wondering why owncloud would want to delete data that is not yet on the server. Scary.

The good news is: The desktop client only deletes local folders, if there is a copy on the server.
The printed warning is overly pessimistic. Please adjust the text, to say e.g:

Unchecked folders that exist on the server will be removed from your local filesystem and will not be synchronized to this computer anymore.

[ogoffart]

I think the current wording is fine.
The fact that some files cannot be removed because they were modified or added will result in errors later anyway.

[TheOneRing]

Removed in #11517