Update self-service-vm-import-ovf-requirements.md
Update self-service-vm-import-ovf-requirements.md

Added the note that the dash character is not allowed in the OVF file name.
eschubert/PublicKB,BobStolzberg/PublicKB,anthonyvetter/PublicKB,adamd/PublicKB,maxim-clc/PublicKB,BryGittyUp/PublicKB,jmalmadclc/PublicKB,keithresar/clc_public_kb,jwcolbert/PublicKB,DLM1/PublicKB,mark-turpin/PublicKB,robertlesieur/PublicKB,jtowns3/PublicKB,duvander/PublicKB,ack/PublicKB,robcaldwell/PublicKB,appfog/PublicKB,ryanbrockman/PublicKB,mfar78/PublicKB,leporaj/PublicKB,StephanieWong/PublicKB,justinwithington/PublicKB,jwebs1/PublicKB,daveshac/PublicKB