fix: correct Ds loss wiring and scheduler hookup

[Lauenburg]

While reviewing the public code, I found that the Ds update incorrectly uses Dy’s optimizer and scheduler.
Effect: Ds never updates. Dy steps twice per iteration and its LR decays twice. This can distort the seg-adversarial signal and weaken translation quality.

Current:

loss_Ds = self.update_netD(self.Ds, real_seg, self.image_pool['Ds'].query(fake_seg),
                           self.optimizer['Dy'], self.lr_scheduler['Dy'])

Fix:

loss_Ds = self.update_netD(self.Ds, real_seg, self.image_pool['Ds'].query(fake_seg),
                           self.optimizer['Ds'], self.lr_scheduler['Ds'])