fdo#78004 fix string formatting

Added missing 's'

Change-Id: I7570d86d65ebcffc547b06ab9c19843de0b90436
Reviewed-on: https://gerrit.libreoffice.org/9181
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>