docs: update `tns migrate` docs based on the latest changes
docs: update `tns migrate` docs based on the latest changes

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