fix(postfix): use param $2 of _parse_help

Author: akinomyoga

completions/postfix

@@ -17,11 +17,8 @@ _comp_cmd_postfix()
     esac
 
     if [[ $cur == -* ]]; then
-        COMPREPLY=($(
-            compgen -W \
-                '$(_bashcomp_try_faketty "$1" --help 2>&1 | _parse_usage -)' \
-                -- "$cur"
-        ))
+        COMPREPLY=($(compgen -W \
+            '$(_parse_usage _bashcomp_try_faketty "$1 --help")' -- "$cur"))
         return
     fi