Replaced deprecated UDSEntry::insert with UDSEntry::fastInsert

With KIO 5.48 UDSEntry::insert is deprecated in favor of
UDSEntry::fastInsert. This patch fixes all warnings related to the change
in KIO.

Authored by: Nikita Melnichenko, Davide Gianforte.

FIXED: UDSEntry::insert deprecation warnings

Differential Revision: https://phabricator.kde.org/D15376

(cherry picked from commit a7ebda9a8054448f46feb044935236c86021bc29)