CI test linux://python/ray/dag:test_torch_tensor_transport_gpu is consistently_failing

[aslonnie]

CI test linux://python/ray/dag:test_torch_tensor_transport_gpu is consistently_failing. Recent failures:
- https://buildkite.com/ray-project/postmerge/builds/17105#019d9d73-1adf-4b75-8e91-3261ed90075f
- https://buildkite.com/ray-project/postmerge/builds/17105#019d9d0d-2328-4ecb-9db1-9b9599898509
- https://buildkite.com/ray-project/postmerge/builds/17105#019d9d0d-2328-4d92-99f1-db6ced27c552
- https://buildkite.com/ray-project/postmerge/builds/17098#019d9cac-e3c9-40fd-903e-f25e57d386df
- https://buildkite.com/ray-project/postmerge/builds/17098#019d9cb2-f848-4ff9-ba51-2e6f386ac633

DataCaseName-linux://python/ray/dag:test_torch_tensor_transport_gpu-END
Managed by OSS Test Policy

[aslonnie]

This test is now considered as flaky because it has been failing on postmerge for too long. Flaky tests do not run on premerge.