Fix flaky issue detail spec
What does this MR do and why?
Visit the blank page before switching users to prevent CSRF errors from AJAX requests triggered from the previously loaded page.
In https://gitlab.com/gitlab-org/gitlab-foss/-/jobs/6884064233, the POST
request to POST /-/track_namespace_visits
fails.
MR acceptance checklist
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Related to #437351 (closed)
Edited by Heinrich Lee Yu