fdo#65836 Do not compress WMF / EMF file incase of OOXML export

Change-Id: Ic498e5703ab48719f998be6da3f245843cc0979d
Reviewed-on: https://gerrit.libreoffice.org/6849
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>