CI test linux://doc:doctest[train-gpu][gpu] is consistently_failing

[can-anyscale]

CI test linux://doc:doctest[train-gpu][gpu] is consistently_failing. Recent failures:
- https://buildkite.com/ray-project/postmerge/builds/9155#0195d586-7492-4d33-b941-a922e67c0c94
- https://buildkite.com/ray-project/postmerge/builds/9155#0195d4eb-07bc-42fa-9fc1-a73d9e359e42

DataCaseName-linux://doc:doctest[train-gpu][gpu]-END
Managed by OSS Test Policy

[can-anyscale]

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

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Blamed commit: 8ed6823 found by bisect job https://buildkite.com/ray-project/release-tests-bisect/builds/2164

[aslonnie]

reverted: #51754

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Test passed on latest run: https://buildkite.com/ray-project/postmerge/builds/9165#0195d85d-d175-489e-b36f-5427b201112e

[can-anyscale]

Test passed on latest run: https://buildkite.com/ray-project/postmerge/builds/9170#0195d93b-ba02-45c6-95db-39d668fbd91f