CO "Supply Chain Security Fundamentals" course updates

[sheesh]

This is an issue for implementing feedback given by reviewers from CS and other teams.

Feedback can be found in this thread in the temp-customer-onboarding channel:https://chainguard-dev.slack.com/archives/C07BF1VRL1E/p1725476038771929

Make sure to also check the Google Doc (in the customer onboarding spreadsheet) for each article to see if there is any additional feedback.