fix typo Sufface->Surface

Change-Id: I90847d0edbc2c13e405562647b150012bc5df7e2
Reviewed-on: https://gerrit.libreoffice.org/11249
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>