[caffe2] Update shape info delimiter (#39275)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/39275
Replace delimiter '|' with '#' because '|' could appear in the tensor names.
Test Plan:
```
buck test //caffe2/caffe2/fb/opt:shape_info_utils_test
```
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Reviewed By: yinghai
Differential Revision: D21781037
fbshipit-source-id: f83497b12ddf0e7b71d6aed0e20873d52e97fb7f
