sftpd: remove workarounds for directory listing

The underlying issue was fixed in pkg/sftp 1.13.2

vfs/sys_unix.go

@@ -4,33 +4,10 @@ package vfs
 
 import (
 	"errors"
-	"os"
-	"syscall"
 
 	"golang.org/x/sys/unix"
 )
 
-var (
-	defaultUID, defaultGID int
-)
-
-func init() {
-	defaultUID = os.Getuid()
-	defaultGID = os.Getuid()
-	if defaultUID < 0 {
-		defaultUID = 65534
-	}
-	if defaultGID < 0 {
-		defaultGID = 65534
-	}
-}
-
-func (fi FileInfo) getFileInfoSys() interface{} {
-	return &syscall.Stat_t{
-		Uid: uint32(defaultUID),
-		Gid: uint32(defaultGID)}
-}
-
 func isCrossDeviceError(err error) bool {
 	return errors.Is(err, unix.EXDEV)
 }