Ensure empty ints attributes are created correctly

[justinchuby]

Changes due to onnx/ir-py#148

_______________ ShapeOptimizationTest.test_shape_optimization_5 ________________
[gw0] darwin -- Python 3.11.9 /Users/runner/work/onnxscript/onnxscript/.nox/test_onnx_ir_git/bin/python
.nox/test_onnx_ir_git/lib/python3.11/site-packages/parameterized/parameterized.py:620: in standalone_func
    return func(*(a + p.args), **p.kwargs, **kw)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript/rewriter/ort_fusions/shape_optimization_test.py:58: in test_shape_optimization
    count = shape_optimization.rules.apply_to_model(model)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript/rewriter/_rewrite_rule.py:768: in apply_to_model
    count = self._apply_to_graph_or_function(
onnxscript/rewriter/_rewrite_rule.py:659: in _apply_to_graph_or_function
    delta = rule.try_rewrite(
onnxscript/rewriter/_rewrite_rule.py:323: in try_rewrite
    replacement_subgraph = self._replacement_pattern.get_replacement(match)
                           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript/rewriter/_rewrite_rule.py:219: in get_replacement
    new_outputs = self._function(context, **match.bindings)
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript/rewriter/ort_fusions/shape_optimization.py:58: in rewrite
    return op.Constant(value_ints=[])
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript/ir/_tape.py:23: in <lambda>
    return lambda *args, **kwargs: self._make_node(op_type, args, kwargs)
                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
onnxscript/ir/_tape.py:36: in _make_node
    value = super().op(
.nox/test_onnx_ir_git/lib/python3.11/site-packages/onnx_ir/_tape.py:92: in op
    attrs = _convenience.convert_attributes(attributes)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.nox/test_onnx_ir_git/lib/python3.11/site-packages/onnx_ir/_convenience/__init__.py:270: in convert_attributes
    attributes.append(convert_attribute(name, attr))
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
.nox/test_onnx_ir_git/lib/python3.11/site-packages/onnx_ir/_convenience/__init__.py:148: in convert_attribute
    attr_type = _infer_attribute_type(attr)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^
.nox/test_onnx_ir_git/lib/python3.11/site-packages/onnx_ir/_convenience/__init__.py:73: in _infer_attribute_type
    raise ValueError(
E   ValueError: Cannot infer type of empty sequence. Please create an Attr with an explicit type.