Merge branch 'branch-0.5.0' into 'branch-0.5.0'

Update CONTRIBUTING.md

See merge request megasearch/milvus!611

Former-commit-id: 1b1eed65ab1dcf4758ad8d26d5bbe490be0b1673

cpp/CONTRIBUTING.md

@@ -49,7 +49,7 @@ And we made the following changes based on the guide:
 - 4 spaces for indentation
 - Adopt .cpp file extension instead of .cc extension
 - 120-character line length
-- The file name starts with the upper case
+- Camel-Cased file names
 
 
 ## Run unit test