Update instructions on License Monitoring

Improve the onboarding task guidance on getting new Sandbox projects to import their repos into either CNCF Snyk or CNCF FOSSA.

We want new maintainers

1. to add fossa or snyk labels to their ob issues express their service preference
2. not setup accounts on these services, we do that
3. to understand that as these sevices integrate with GitHub, the email addresses that we use to send invitations ideally need to be associated with the GitHub acccounts that they you for their open source work.