Add docstring for is_inference_mode_enabled (#59047)
Summary:
Fixes` #{issue number}
Testing:
```
>>> import torch
>>> torch.is_inference_mode_enabled.__doc__
'\nis_inference_mode_enabled(input) -> (bool)\n\nReturns True if inference mode is currently enabled.\n\nArgs:\n input (Tensor): the input tensor.\n'
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/59047
Reviewed By: ailzhang
Differential Revision: D28726991
Pulled By: soulitzer
fbshipit-source-id: c117c7d73e551a1b5f0e215f2aed528bf558ef7c
