Fix opset import in GemmFloat8 python unit tests (microsoft#18489)

### Description
The unit test are failing if a development version of onnx is used. The
opset are set to 19.

onnxruntime/test/python/onnxruntime_test_float8_gemm8.py

@@ -14,6 +14,7 @@
 from numpy.testing import assert_allclose
 from onnx import TensorProto
 from onnx.checker import check_model
+from onnx.defs import onnx_opset_version
 from onnx.helper import make_graph, make_model, make_node, make_opsetid, make_tensor_value_info
 from onnx.numpy_helper import from_array
 
@@ -91,7 +92,10 @@ def get_model_gemm(
         ]
         nodes = [n for n in nodes if n is not None]
         graph = make_graph(nodes, "gemm", inputs, [d], inits)
-        onnx_model = make_model(graph, opset_imports=[make_opsetid("", 19)], ir_version=9)
+        opset_imports = [make_opsetid("", onnx_opset_version() - 1)]
+        if domain == "com.microsoft":
+            opset_imports.append(make_opsetid("com.microsoft", 1))
+        onnx_model = make_model(graph, opset_imports=opset_imports, ir_version=9)
         if domain != "com.microsoft":
             check_model(onnx_model)
         return onnx_model
@@ -268,7 +272,8 @@ def test_combinations(self, shapeA, shapeB, transA, transB):
                     make_tensor_value_info("B", TensorProto.FLOAT, [None, None]),
                 ],
                 [make_tensor_value_info("Y", TensorProto.FLOAT, [None, None])],
-            )
+            ),
+            opset_imports=[make_opsetid("", 19), make_opsetid("com.microsoft", 1)],
         )
 
         sess = InferenceSession(model.SerializeToString(), providers=["CUDAExecutionProvider", "CPUExecutionProvider"])