Merge pull request #5220 from cs2be/UPDATE_CONTRIBUTION_FOR_SPHINX

Update CONTRIBUTION.md to generate correctly on SPHINX

Author: cs2be

CONTRIBUTING.md

@@ -151,12 +151,7 @@ python \
 
 This will enable VLOG messages generated by `buddy_allocator.{h,cc}` and in the verbose range of 0 to 3, so you will see above example VLOG message, which is in level 3.  This suggests that we output overall messages in lower verbose levels, so they display with higher probability.  When coding C++, please follow the verbose level convention as follows:
 
-- verbose level 1:
-  - [framework](https://github.com/PaddlePaddle/Paddle/tree/develop/paddle/framework)
-- verbose level 3:
-  - [operators](https://github.com/PaddlePaddle/Paddle/tree/develop/paddle/operators)
-- verbose level 5:
-  - [memory](https://github.com/PaddlePaddle/Paddle/tree/develop/paddle/memory)
-  - [platform](https://github.com/PaddlePaddle/Paddle/tree/develop/paddle/platform)
-- verbose level 7:
-  - [math](https://github.com/PaddlePaddle/Paddle/tree/develop/paddle/math)
+- verbose level 1: [framework](https://github.com/PaddlePaddle/Paddle/tree/develop/paddle/framework)
+- verbose level 3: [operators](https://github.com/PaddlePaddle/Paddle/tree/develop/paddle/operators)
+- verbose level 5: [memory](https://github.com/PaddlePaddle/Paddle/tree/develop/paddle/memory), [platform](https://github.com/PaddlePaddle/Paddle/tree/develop/paddle/platform)
+- verbose level 7: [math](https://github.com/PaddlePaddle/Paddle/tree/develop/paddle/math)

doc/howto/dev/contribute_to_paddle_en.md

@@ -0,0 +1 @@
+../../../CONTRIBUTING.md

doc/howto/index_cn.rst

@@ -21,7 +21,6 @@
 
   dev/build_cn.rst
   dev/write_docs_cn.rst
-  dev/contribute_to_paddle_cn.md
 
 模型配置
 --------