Clarifying "adoption" in onboarding checklist for CLA/DCO

[mlaurencin]

In today's working session, there was a discussion on better defining "adoption" in the onboarding guidelines. The discussion itself was due to the usage relating to the CoC policy, however the terminology is also used for the item:

• Adopt either the Contributor License Agreement (CLA) or the Developer Certificate of Origin (DCO)

The work related to the CoC policy is captured in issue #1255 where a comment was made in regard to the working group discussion. This issue is capturing the CLA/DCO aspect of the guidelines specifically.