Op info test for `constant_pad_nd`

[qihqi]

Fix the Op info test for constant_pad_nd

1. Find the line 33 of test_ops.py and remove constant_pad_nd from skip_list
2. Run op_info test with pytest test/test_ops.py
3. Fix the failure.

Please refer to this guide as guide to fix:

Also refer to these PRs:

• https://github.com/pytorch/xla/pull/7343
• https://github.com/pytorch/xla/pull/7312
• https://github.com/pytorch/xla/pull/7325