Update

Signed-off-by: Jael Gu <mengjia.gu@zilliz.com>

README.md

@@ -17,7 +17,7 @@ Barlas Oğuz, Sewon Min, Patrick Lewis, Ledell Wu, Sergey Edunov, Danqi Chen, We
 In this work, we show that retrieval can be practically implemented using dense representations alone,
 where embeddings are learned from a small number of questions and passages by a simple dual-encoder framework[2].
 
-## Reference
+### References
 
 [1].https://huggingface.co/docs/transformers/model_doc/dpr