fix: show preferred commit email in empty project page

What does this MR do?

This is a follow-up to #43521 (closed). It shows the preferred commit email in the git setup instruction, instead of the user's default email.

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry for user-facing changes, or community contribution. Check the link for other scenarios.
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Performance and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Security

Not applicable.