docs: update migrate help
docs: update migrate help

NativeScript/nativescript-cli,NativeScript/nativescript-cli,NathanaelA/nativescript-cli,NathanaelA/nativescript-cli,NativeScript/nativescript-cli,NativeScript/nativescript-cli,NathanaelA/nativescript-cli,NathanaelA/nativescript-cli