Fix creating labels for Jira import

What does this MR do?

We introduced importing labels as proper labels for Jira import (instead of appending them to description which we did before).

I, however, apparently committed one change to another branch and didn't notice it is missing from the original MR. Therefore labeling issues is now broken.

The problem is that we can't assign label attributes to an object we want to create when using bulk_import and we need to create label links separately. This MR fixes that.

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.