Update font-awesome icons in prometheus config

What does this MR do?

This replaces the font-awesome icons for the prometheus configuration inside the integrations settings

#282425 (closed)

Screenshots (strongly suggested)

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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