Resolve "Update “cannot merge” icon color on avatars"

What does this MR do?

• Update icon color to use a lighter orange ($orange-400, #C17D10).
• Ensure the orange meets a 3:1 contrast ratio on the background (#fafafa in this case).

Note: This will look darker, and generally more brown than the previous orange (#de7e00), but this is necessary to meet a 3:1 contrast ratio and satisfy WCAG SC 1.4.11 Non-text Contrast.

Before	After

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

N/A

Security

N/A

Closes #247132 (closed)