fix split shape inference error for opset >= 13 (microsoft#19756)

### Description
get split operator split section by opset

### Motivation and Context
for opset higher than 13, split section is treated as an input.

onnxruntime/python/tools/symbolic_shape_infer.py

@@ -1940,8 +1940,17 @@ def _infer_SoftmaxCrossEntropyLoss(self, node):  # noqa: N802
     def _infer_Split_Common(self, node, make_value_info_func):  # noqa: N802
         input_sympy_shape = self._get_sympy_shape(node, 0)
         axis = handle_negative_axis(get_attribute(node, "axis", 0), len(input_sympy_shape))
-        split = get_attribute(node, "split")
-        if not split:
+        op_set = get_opset(self.out_mp_)
+
+        # Depending on op-version 'split' are provided as attribute or via 2nd input
+        if op_set < 13:
+            split = get_attribute(node, "split")
+            assert self._try_get_value(node, 1) is None
+        else:
+            split = self._try_get_value(node, 1)
+            assert get_attribute(node, "split") is None
+
+        if split is None:
             num_outputs = len(node.output)
             split = [input_sympy_shape[axis] / sympy.Integer(num_outputs)] * num_outputs
             self._update_computed_dims(split)