[TensorBoard] Fixes missing doc for add_graph (#37504)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/37415
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37504
Differential Revision: D21305979
Pulled By: natalialunova
fbshipit-source-id: 0606a39a6006a236a37a0e6df87959736474547f
