Fixed the y_label not setting correctly for each graph on the monitoring dashboard

What does this MR do?

Fixes the y_label not being set in the new monitoring dashboard for each graph

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

None at the moment

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• 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?

closes #34599 (closed)