Simplify _filedir arguments.

contrib/mcrypt

@@ -58,12 +58,12 @@ _mcrypt()
             --list-hash --verbose --quiet --help \
             --version --license' -- "$cur" ) )
     elif [[ ${COMP_WORDS[0]} == mdecrypt ]]; then
-        _filedir '@(nc)'
+        _filedir nc
     else
         decrypt=0
         for (( i=1; i < ${#COMP_WORDS[@]}-1; i++ )); do
             if [[ ${COMP_WORDS[i]} == -@(d|-decrypt) ]]; then
-                _filedir '@(nc)'
+                _filedir nc
                 decrypt=1
                 break
             fi