Add missing function call that causes related merge requests spinner to never resolve

What does this MR do?

For #9013 (closed).

This adds a function call that correctly fetches any related merge requests for a commit and replaces the spinner on the commit pipelines page.

Context

I'm not sure why this function wasn't already here: all of the code already existed, it just wasn't called for the pipelines page, while it was called for the main commit page.

In any case, there's zero new logic here: just importing an existing function and calling it when the tab loads.

Screenshots

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

• 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