Added hint about the execution order of before_script and artifact restoration.

What does this MR do?

It improves the documentation, concerning the order of the before_script and artifact restoration.

Are there points in the code the reviewer needs to double check?

I don't think so, it's just markdown.

Why was this MR needed?

Others might have the same question.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• [?] Changelog entry added is this also necessary for minor documentation changes? please contact me if so.
• Documentation created/updated
• [-] API support added
• Tests
  • [-] Added for this feature/bug
  • [-] All builds are passing
• [-] Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

None.