Fix explain this vulnerability spec

What does this MR do and why?

Relates to #468869 (closed) and https://gitlab.com/gitlab-org/gitlab/-/issues/471101

Addresses: #468642 (closed)

MR acceptance checklist

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Before	After

How to set up and validate locally

GITLAB_ADMIN_USERNAME=gitlab-qa-bot GITLAB_ADMIN_PASSWORD="<password>" GITLAB_QA_ACCESS_TOKEN=token GITLAB_USERNAME=gitlab-qa GITLAB_PASSWORD="<password>" GITLAB_QA_USER_AGENT="user_agent" WEBDRIVER_HEADLESS=false QA_DEBUG=true QA_GITLAB_URL=https://staging.gitlab.com QA_COOKIES="gitlab_canary=true" bundle exec rspec ./qa/specs/features/ee/browser_ui/10_govern/explain_this_vulnerability_spec.rb:63