fix test_backward_node_failure flakiness (#31588)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/31588
Per title. This test can sometimes fail with a different error regex
than the one that is currently tested, so add this error regex to make the test
pass consistently.
Differential Revision: D19222275
fbshipit-source-id: 89c95276d4d9beccf9e0961f970493750d78a96b
