Display files in tab counter same as diff stats

Issue > #33849 (closed)

What does this MR do?

The MR ensures the text listed in the diff stat matches the text in the "Changes" tab.

Before	After

Testing Case

1. Go to a Merge Request > Click "Changes" tab

• The text in "changes" tab matches the text in the diff stat.

Truncated

• It displays the + in the diff stat, which matches the "changes" tab

Full number

• It displays the full number in the diff stat, which matches the "changes" tab

Empty

• It doesn't display any number when it's empty

Screenshots

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

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

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 #33849 (closed)