Update GettingStarted doc to use `--scheme` for update-checkout script
Update GettingStarted doc to use `--scheme` for update-checkout script

https://bugs.swift.org/browse/SR-13717
hooman/swift,roambotics/swift,benlangmuir/swift,roambotics/swift,gregomni/swift,benlangmuir/swift,tkremenek/swift,JGiola/swift,apple/swift,gregomni/swift,glessard/swift,benlangmuir/swift,hooman/swift,ahoppen/swift,jmgc/swift,jmgc/swift,jmgc/swift,JGiola/swift,jmgc/swift,parkera/swift,rudkx/swift,tkremenek/swift,xwu/swift,glessard/swift,parkera/swift,JGiola/swift,tkremenek/swift,xwu/swift,atrick/swift,xwu/swift,hooman/swift,xwu/swift,jmgc/swift,xwu/swift,tkremenek/swift,jmgc/swift,parkera/swift,atrick/swift,apple/swift,atrick/swift,rudkx/swift,roambotics/swift,parkera/swift,ahoppen/swift,tkremenek/swift,ahoppen/swift,apple/swift,tkremenek/swift,glessard/swift,ahoppen/swift,hooman/swift,atrick/swift,ahoppen/swift,tkremenek/swift,glessard/swift,gregomni/swift,JGiola/swift,rudkx/swift,glessard/swift,benlangmuir/swift,JGiola/swift,apple/swift,apple/swift,xwu/swift,parkera/swift,xwu/swift,atrick/swift,gregomni/swift,hooman/swift,parkera/swift,rudkx/swift,atrick/swift,hooman/swift,ahoppen/swift,roambotics/swift,roambotics/swift,benlangmuir/swift,glessard/swift,gregomni/swift,parkera/swift,JGiola/swift,apple/swift,hooman/swift,jmgc/swift,gregomni/swift,parkera/swift,rudkx/swift,roambotics/swift,rudkx/swift,benlangmuir/swift