Fix merge request count for role based rendering

What does this MR do and why?

Fixes the count for merge requests in the nav bar when the user has the merge request dashboard to render as role based.

References

Screenshots or screen recordings

How to set up and validate locally

• Open https://gdk.test:3000/dashboard/merge_requests
• Click the preference dropdown in the top right of the page
• Change to Role rendering
• Notice the count
• Change back to Workflow and the count should be different if there is any merge requests in Waiting for approvals

MR acceptance checklist

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