display too small arrow to the appropriate size

: Visio implementation-dependent problem

Change-Id: I15131cafd82429b18874fa69a149deb8bee00e0c
Reviewed-on: https://gerrit.libreoffice.org/12523
Reviewed-by: Fridrich Strba <fridrich@documentfoundation.org>
Tested-by: Fridrich Strba <fridrich@documentfoundation.org>