specify protobuf version (#2406)

tianxin · web-flow · commit 7d1d6fe3ac68 · 2022-06-02T20:23:38.000+08:00
* update pipeline README

* specify protobuf version
diff --git a/requirements.txt b/requirements.txt
@@ -9,3 +9,4 @@ tqdm
 paddlefsl
 sentencepiece
 paddle2onnx
+protobuf>=3.1.0, <=3.20.0
