Fix 'duplicate alerts' for security issues in comments. Although thes…

…e are unique alerts it isn't obvious from the UI and will be obvious if the package link is followed

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@@ -153,7 +153,8 @@ def create_security_alert_table(diff: Diff, md: MdUtils) -> (MdUtils, list, dict
  ", ".join(sources),
  manifest_str
  ]
- alert_table.extend(row)
+ if row not in alert_table:
+ alert_table.extend(row)
  num_of_alert_rows = len(diff.new_alerts) + 1
  md.new_table(
  columns=num_of_alert_columns,