added set_printoptions examples (#68324)
Summary:
Added examples for `torch.set_printoptions`
```
>>> torch.set_printoptions(precision=2)
>>> torch.tensor([1.12345])
tensor([1.12])
>>> torch.set_printoptions(threshold=5)
>>> torch.arange(10)
tensor([0, 1, 2, ..., 7, 8, 9])
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68324
Reviewed By: ngimel
Differential Revision: D33063869
Pulled By: anjali411
fbshipit-source-id: 24db99df1419f96ba8ae2b5217cb039b288b630a
