Fix to show renamed file in mr

What does this MR do?

Issue: https://gitlab.com/gitlab-org/gitlab-ce/issues/59786

When you rename an existing file and make some changes to it. The old file name is no longer shown, only the new name is displayed. This MR fixes that. Where the old and new file name will be both displayed.

Testing Case

1. Navigate to a Merge Request
2. Click on "Open in Web IDE"
3. This will launch the editor
4. Find a random file and rename it
5. Commit the changes
6. Find that renamed file and insert a line of text
7. Commit the changes
8. Navigate back to the Merge Request
9. Click on the "Changes" tab

• The header should include the updated file name as well as the old one

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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

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #59786 (closed)