Change debug log output color to magenta

What does this MR do?

Changes the debug log messages displayed when SECURE_LOG_LEVEL: debug is configured from blue to magenta, because blue is really difficult to read on a black background.

Screenshots or screen recordings

Before	After

What are the relevant issue numbers?

N/A

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added for this feature/bug
• Job definition updated, if necessary
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• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Security reports checked/validated by reviewer