Update repo_guidelines.md (#4306)
Update repo_guidelines.md (#4306)

typo, cla -> dco
Signed-off-by: andife <3b771aa29566868aa6249b9af7dd490850d45d3a@arcor.de>

Co-authored-by: Chun-Wei Chen <3d21e1cad9aa0e4aa10838f859be24690cfc357c@gmail.com>
onnx/onnx,onnx/onnx,onnx/onnx,onnx/onnx