update similarity_net dygraph (#4291)

* Update README.md (#4267)

* test=develop (#4269)

* 3d use new api (#4275)

* PointNet++ and PointRCNN use new API

* Update Readme of Dygraph BERT (#4277)

Fix some typos.

* Update run_classifier_multi_gpu.sh (#4279)

remove the CUDA_VISIBLE_DEVICES

* Update README.md (#4280)

* add similarity_net dygraph

* fix similarity_net dygraph
Co-authored-by: Npkpk <xiyzhouang@gmail.com>
Co-authored-by: NKaipeng Deng <dengkaipeng@baidu.com>