Update closed MRs on push

What does this MR do?

In !29420 (merged), we started filtering the branches that we update on push. It only looks at branches with open MRs.

It caused a regression wherein closed MRs approvals weren't being reset even when reset_approvals_on_push setting is set to true.

This updates the MergeRequests::PushedBranchesService to include closed MRs with matching source branches as well.

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

#225579 (closed)