Added a test case for an index error for the index_copy_ (#21912)
Summary:
Follow up PR with a test for the [fixed](https://github.com/pytorch/pytorch/commit/4b45f08f8765549915417997c30ae8981f2ad125) [bug](https://github.com/pytorch/pytorch/issues/20322).
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21912
Differential Revision: D15878674
Pulled By: izdeby
fbshipit-source-id: c8fef2214606c796d174d0faaaf633531a7bea88
