Update Severity

Update the raw 0-10 severity of a single issue. The rating shown on the issue is the composite ZeroPath score (severity x confidence, 0-100), so the rating follows the severity only for a finding a scanner agent actually assessed. A finding with no recorded confidence is scored on its severity alone, which keeps it in the Informational band whatever severity you set; use issues.updateSeverityRating to move the rating of one of those.