Update install-toolchain.sh

Author: MaxDesiatov

scripts/install-toolchain.sh

@@ -19,7 +19,6 @@ fi
 case $(uname -s) in
   Darwin)
     toolchain_download="$swift_tag-macos_x86_64.pkg"
-    echo '-macos' >> .swift-version
   ;;
   Linux)
     if [ $(grep RELEASE /etc/lsb-release) == "DISTRIB_RELEASE=18.04" ]; then