Removes an unneeded placeholder cell altogether from the collection view.
- iOS 11.0+
- Mac Catalyst 13.0+
YES if the placeholder cell was removed, or
NO if the cell was no longer in the collection view.
Use this method to remove a placeholder cell without swapping in a new cell. You might call this method if the user chooses to undo the insertion of a cell or if the contents of the collection view changed.