Add missing entry for sampled_addmm in sparse.rst (#72312)
Summary:
Let's make the documentation for `torch.sparse.sampled_addmm` searchable in the PyTorch documentation.
This PR shall be cherry-picked for the next 1.11 release.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/72312
Reviewed By: davidberard98
Differential Revision: D34045230
Pulled By: cpuhrsch
fbshipit-source-id: c1b1dc907443284857f48c8ce1efab22c6701bbe
(cherry picked from commit 225929ecf20eb369f862b091818f5af16ee78f88)
