Fix broken link to observatory cli on Frontend Dev Guide

What does this MR do?

• Fix broken link to the observatory cli on the Frontend Developer Guide

Why was this MR needed?

• To properly direct Frontend devs to the observatory cli resource which may assist them with security best practices.

Does this MR meet the acceptance criteria?

• Changelog entry added
• 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