[E2E] Verify that dismissed vulnerabilities do not show up in MR widget

What does this MR do and why?

• Adds a spec to validate that dismissed vulnerabilities do NOT show up in a new MR security widget. Relates to: gitlab-org/quality/quality-engineering/team-tasks#1767 (closed)
• Also fixes an existing broken change_state function to account for changing to dismissed status.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

WEBDRIVER_HEADLESS=false GITLAB_QA_ACCESS_TOKEN=xxxx GITLAB_PASSWORD="XXXX" QA_LOG_LEVEL=DEBUG QA_GITLAB_URL=http://192.168.86.46:3000 bundle exec rspec  ./qa/specs/features/ee/browser_ui/10_govern/dismissed_vulnerabilities_in_security_widget.rb

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.