Update tag format guidance for GitHub Actions

[kbukum1]

Clarify tag format recommendations for GitHub Actions in monorepos.

Why:

Closes [issue link]

What's being changed (if available, include any code snippets, screenshots, or gifs):

Check off the following:

• I have reviewed my changes in staging (look for the "Automatically generated comment" and click the links in the "Preview" column to view your latest changes).
• For content changes, I have completed the self-review checklist.

[dsotirakis]

Thanks @kbukum1!