Update cross-platform-testing.md
Update cross-platform-testing.md

Small change in command
iamjasonp/wcf,ElJerry/wcf,khdang/wcf,SajayAntony/wcf,shmao/wcf,dotnet/wcf,mconnew/wcf,imcarolwang/wcf,khdang/wcf,mconnew/wcf,ElJerry/wcf,zhenlan/wcf,mconnew/wcf,SajayAntony/wcf,dotnet/wcf,imcarolwang/wcf,StephenBonikowsky/wcf,dotnet/wcf,KKhurin/wcf,MattGal/wcf,imcarolwang/wcf,MattGal/wcf,StephenBonikowsky/wcf,KKhurin/wcf,zhenlan/wcf,ericstj/wcf,hongdai/wcf,hongdai/wcf,ericstj/wcf,shmao/wcf,iamjasonp/wcf