completion: use __gitcomp_builtin in _git_reset

The new completable options are:

--intent-to-add
--quiet
--recurse-submodules
Signed-off-by: NNguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -2685,7 +2685,7 @@ _git_reset ()
 
 	case "$cur" in
 	--*)
-		__gitcomp "--merge --mixed --hard --soft --patch --keep"
+		__gitcomp_builtin reset
 		return
 		;;
 	esac