Mark two velo tests as xfail due to upstream fixes (#1359)
Mark two velo tests as xfail due to upstream fixes (#1359)

https://github.com/GenericMappingTools/gmt/pull/5360 fixes a bug related to velo pen settings. 

Two velo tests fail due to the upstream bug fixes and are marked as "xfail".
GenericMappingTools/gmt-python,GenericMappingTools/gmt-python