Startcenter: Refresh RecentDocsView when select 'Clear list' menu option

Change-Id: I9cbe647563699b9b610661003084d2cd16093f9a
(cherry picked from commit d930cefbe65d8b7f21100fcbf2ddcd977dd15cb1)
Reviewed-on: https://gerrit.libreoffice.org/7304
Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>
(cherry picked from commit f3a075f97f0cb13c0e73b567fb2d25374b147cf4)
Reviewed-on: https://gerrit.libreoffice.org/7356
Reviewed-by: Eike Rathke <erack@redhat.com>
Reviewed-by: Zolnai Tamás <zolnaitamas2000@gmail.com>
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>