Fix cannot merge icon showing in dropdown when user can merge

What does this MR do?

This MR fixes the cannot merge tooltip showing for users who can merge.

What was the cause of the bug?

The root cause of this bug was that the information for the assigned users did not come from the AJAX response, but instead was inserted through some hidden HAML elements. This was noticeable whenever assigned users were not part of the users AJAX response.

Screenshots

Before (on master)	After (in this MR)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

References

• Related to #31386 (closed)