Convert RID_DLG_MAPPING to .ui

Change-Id: I92a5778a2f4f69beb73885c2f7c78a43045986c0
Reviewed-on: https://gerrit.libreoffice.org/9779
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>