fix shellcheck

bin/terractl

@@ -567,7 +567,8 @@ command=$1; shift
 case $command in
   -h|--help|help) usage 0 ;;
   -V|--version|version)
-    if [[ $TERRACTL_VERSION == "@"VERSION"@" ]]; then echo "terractl (development copy)"
+    # The build replaces the placeholder with a version number, which never contains '@'
+    if [[ $TERRACTL_VERSION == *@* ]]; then echo "terractl (development copy)"
     else echo "terractl $TERRACTL_VERSION"; fi
     exit 0 ;;
   list) cmd_list; exit ;;