[UnitTest][Flaky] Increased tolerance on onnx test_forward::test_aten

Default tolerance had about 2-3% failure rate (8/300 iterations), and
caused failures on unrelated PRs
(e.g. https://ci.tlcpack.ai/blue/organizations/jenkins/tvm/detail/PR-8784/1/pipeline#step-485-log-1156).
New limit of `atol=5e-7` chosen to be above the maximum delta of
3.5e-7 observed in 300 iterations.

tests/python/frontend/onnx/test_forward.py

@@ -5056,7 +5056,7 @@ def verify_embedding_bag(num_embedding, embedding_dim, data_shape, num_bags=None
             target=target,
             dev=dev,
         )
-        tvm.testing.assert_allclose(torch_out.numpy(), tvm_out)
+        tvm.testing.assert_allclose(torch_out.numpy(), tvm_out, atol=5e-7)
 
     verify_embedding_bag(10, 3, [2, 10])
     verify_embedding_bag(32, 2, [3, 3])