WIP: Update test with an additional expectation

What does this MR do?

Adds an extra expectation before the one where the count happens to give time for the second avatar to be shown in the list of assignees.

I'll run the test a few times on CI before asking for a review, to ensure that the test is not flaky, and if it continues with the flakiness, I'll quarantine it for further investigation.

Screenshots

Screenshot taken on CI when the test failed.

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