Fix docstring inconsistencies: string -> str, boolean -> bool (#82410)
### Description
Throughout the PyTorch docs and codebase, the `string` type in docstrings is referred to by two separate names. This leads to inconsistent docs, like you can see here: https://pytorch.org/docs/stable/generated/torch.nn.Conv3d.html#torch.nn.Conv3d
This PR fixes this issue by ensuring that all mentions of the string type in docstrings, are using the same format that Sphinx generates hyperlinks for.
### Testing
No testing should be required for this change
Pull Request resolved: https://github.com/pytorch/pytorch/pull/82410
Approved by: https://github.com/jbschlosser
