Correct LBFGS tolerance_grad doc string (#99792)
LBFGS' `tolerance_grad` parameter has had a default value of `1e-7` since #25240. The doc string wasn't updated in that PR to match the change https://github.com/pytorch/pytorch/blob/main/torch/optim/lbfgs.py#L207.
no open issue for it, just happened to set it to 1e-7 and was surprised my results didn't change :-) eventually noticed inconsistency in the doc and seemed like an easy opportunity to figure out how to contribute.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/99792
Approved by: https://github.com/janeyx99
