Don't error on wrong MR IID in changelog when 'feature flag' is set

What does this MR do?

Relate to: #251086

Don't error on wrong MR IID in changelog when feature flag label is set, based on !42576 (comment 414248194), !42576 (comment 414966745) and !42573 (comment 414197505)

This solves a problem with the change log when using feature flags in Community contribution.
This problem is happening with the MR (!40198 (merged)) I submitted.

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