Add shape inference to SparseLengthsSumSparse ops (#43181)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/43181
att
Test Plan:
```
buck test caffe2/caffe2/opt:bound_shape_inference_test
```
Reviewed By: ChunliF
Differential Revision: D23097145
fbshipit-source-id: 3e4506308446f28fbeb01dcac97dce70c0443975
