Fix scrolling to renamed file when using the rename dialog

Summary:
The `RenameDialog::slotResult()` slot is currently never called because
the dialog is deleted first, due to the usage of the `WA_DeleteOnClose`
attribute. This breaks the scroll-to-renamed-file feature when the
inline renaming is disabled.

Instead of deleting the dialog on close, we can use `deleteLater()` when
we are sure the dialog has actually finished its job, which is when the
KIO move job emits the `result` signal.

Test Plan:
- Disable inline renaming
- Rename a file so that it goes out of the view
- Check whether the view scrolls to the renamed file.

Reviewers: #dolphin, emateli

Subscribers: kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D13304