Fixed failing Issue Analytics QA spec

What does this MR do and why?

Fixes failing Issue Analytics QA spec when issues_completed_analytics_feature_flag feature flag is enabled (see gitlab-org/release/tasks#6460 (closed))

Screenshots or screen recordings

No visual changes.

How to set up and validate locally

1. Feature.enable(:issues_completed_analytics_feature_flag)
2. bundle exec rspec qa/specs/features/ee/browser_ui/2_plan/issues_analytics/issues_analytics_spec.rb and make sure the tests pass
3. Feature.disable(:issues_completed_analytics_feature_flag)
4. Repeat Step 2

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Closes #424661 (closed)