Update variants.avdl
Update variants.avdl

small wordsmithing, so it's merge-ready into master
pcingola/schemas,ga4gh/schemas,heuermh/ga4gh-schemas,dcolligan/schemas,macieksmuga/schemas,diekhans/ga4gh-schemas,diekhans/ga4gh-schemas,saupchurch/schemas,ga4gh/ga4gh-schemas