Update charts.html.haml

What does this MR do?

Fixes #296853 (closed).

Screenshots (strongly suggested)

Left: master, Right: after this MR

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

No risk is posed.