fix typo (#2475)

TTS/tts/layers/losses.py

@@ -200,7 +200,7 @@ class BCELossMasked(nn.Module):
         return loss
 
 
-class DifferentailSpectralLoss(nn.Module):
+class DifferentialSpectralLoss(nn.Module):
     """Differential Spectral Loss
     https://arxiv.org/ftp/arxiv/papers/1909/1909.10302.pdf"""
 
@@ -335,7 +335,7 @@ class TacotronLoss(torch.nn.Module):
             self.criterion_ga = GuidedAttentionLoss(sigma=ga_sigma)
         # differential spectral loss
         if c.postnet_diff_spec_alpha > 0 or c.decoder_diff_spec_alpha > 0:
-            self.criterion_diff_spec = DifferentailSpectralLoss(loss_func=self.criterion)
+            self.criterion_diff_spec = DifferentialSpectralLoss(loss_func=self.criterion)
         # ssim loss
         if c.postnet_ssim_alpha > 0 or c.decoder_ssim_alpha > 0:
             self.criterion_ssim = SSIMLoss()