fix(carton): remove a branch never happening

The variable `has_command` is always set in this context since the
function should have already been exited from the above loop when
`has_command` is empty.

completions/carton

@@ -36,11 +36,7 @@ _comp_cmd_carton()
     fi
 
     case $prev in
-        --version | -v)
-            return
-            ;;
-        --help | -h)
-            [[ $has_command ]] || _comp_cmd_carton__commands "$1"
+        --version | --help | -[vh])
             return
             ;;
         --cpanfile)