I have installed chef client 12.0.3, on top of it I have install chef-dk version 0.3.5 but why chef-dk is installing chef client version Chef
As I'm a big fan of fixing the error instead of fixing the symptom here is what you can do to be sure the SSL connection works with validation (with a little more detail than coderanger one):
1) Get the server certificate and add it to the cacert.pem file of chef-dk
openssl s_client -showcerts -connect
2) set the env variables for ssl libs:
export SSL_CERT_FILE=/opt/chefdk/embedded/ssl/certs/cacert.pem
Retry your upload and it should work.