Fix CrossEntropyLoss in transformers tutorial (#695)

Signed-off-by: David Pollack <david@i2x.ai>

Author: David Pollack

beginner_source/transformer_tutorial.py

@@ -86,7 +86,7 @@ def forward(self, src):
         src = self.pos_encoder(src)
         output = self.transformer_encoder(src, self.src_mask)
         output = self.decoder(output)
-        return F.log_softmax(output, dim=-1)
+        return output
 
 
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