Update new security dashboard description

What does this MR do and why?

Update new security dashboard description

This updates the new security dashboard description and includes a link to the auto-resolve policy docs.

References

Related #556022

Screenshots or screen recordings

How to set up and validate locally

1. Go to group or project security dashboard (make sure there are no vulnerability management policies in that group or project)
2. Verify you can see the description + alert.
3. Click on Learn more -> you should be redirected to security dashboard docs
4. Click on x in alert, it closes. Refresh page, alert is not visible. Delete local storage key security_dashboard_auto_resolve_alert and refresh.
5. Click on Go to policies, it should redirect to Security Policies page.
6. Click "New policy" and select Vulnerability management policy and create one.
7. Go back to dashboard and verify the alert is not shown.

MR acceptance checklist

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