dev(trace): remove unnecessary judge

- Remove unnecessary judge for arrow

Signed-off-by: Gausshj <kylin_0@qq.com>

Author: gausshj

grassmann_tensor/tensor.py

@@ -510,9 +510,6 @@ def trace(self, trace_pair: tuple[int, int]) -> torch.Tensor:
         if edge_first != edge_end:
             raise ValueError(f"Incompatible edges: {edge_first} and {edge_end}.")
 
-        if tensor.arrow[trace_pair[0]] != tensor.arrow[trace_pair[1]]:
-            tensor = tensor.reverse((trace_pair[1],))
-
         order = list(range(tensor.tensor.dim()))
         order_first = order.pop(trace_pair[0])
         order_end = order.pop(trace_pair[1])