Removed unnecessary transpose in Switch Transformer Routing (#33582)

removed switch transformer routing transpose

src/transformers/models/switch_transformers/modeling_switch_transformers.py

@@ -298,7 +298,7 @@ class SwitchTransformersSparseMLP(nn.Module):
 
         router_mask = router_mask.bool()
         batch_size, seq_len, num_experts = router_mask.shape
-        idx_mask = router_mask.transpose(1, 2).reshape(batch_size * seq_len, num_experts).sum(dim=0)
+        idx_mask = router_mask.reshape(batch_size * seq_len, num_experts).sum(dim=0)
         idx_mask = torch.nonzero(idx_mask, as_tuple=True)[
             0
         ].tolist()  # length: number of "activated" expert / value: index