Adds secdashboard steps to broken_master docs

In a meeting today regarding Omnibus vulnerability management, we decided on a path forward with regards to how the Omnibus team should interact with the security dashboard when triaging dependency updates.

This MR updates the documentation to indicate that we need to link the issue that gets created to the Vulnerability and to change it's status to Confirmed.

I've also added a step to change the Vulnerability to Resolved, although I'm not entirely sure if that's needed 🤔 it might get automatically resolved when the scanner no longer sees it as being updated? Happy to remove it now (or later) once we know what the behavior is.