Fix `sequence_ops_test` (#72844)
Summary:
Fuzzing gone bad again: `np.unique([])` returns array or float64, but `np.delete` expects array of int
Fixes recent regressions in ONNX tests in OSS CI, see https://github.com/pytorch/pytorch/runs/5188636426?check_suite_focus=true for example
Pull Request resolved: https://github.com/pytorch/pytorch/pull/72844
Reviewed By: gmagogsfm
Differential Revision: D34235295
Pulled By: malfet
fbshipit-source-id: 37ad39ac04f81ac519a5d4e4e8a86901944973bd
(cherry picked from commit 683c767e72dad70a12297545a1b9345c89add3c4)
