update-bash: stop handling command name argument

Library/Homebrew/cmd/update-bash.sh

@@ -228,7 +228,6 @@ update-bash() {
   for option in "$@"
   do
     case "$option" in
-      update|update-bash) shift ;;
       --help) brew update --help; exit $? ;;
       --verbose) HOMEBREW_VERBOSE=1 ;;
       --debug) HOMEBREW_DEBUG=1;;