fix: remove shift to prevent error when no arguments in Zsh

When no arguments are provided, Zsh reports "shift count must be <= $#".
Removing the shift ensures clashhelp works correctly in both Bash and Zsh
without producing any error messages.

script/clashctl.sh

@@ -354,7 +354,6 @@ function clashctl() {
         clashupgrade "$@"
         ;;
     *)
-        shift
         clashhelp "$@"
         ;;
     esac