Do not report ghost package as latest/next non-vulnerable version

Signed-off-by: Keshav Priyadarshi <git@keshav.space>

vulnerabilities/models.py

@@ -632,7 +632,7 @@ def only_vulnerable(self):
         return self._vulnerable(True)
 
     def only_non_vulnerable(self):
-        return self._vulnerable(False)
+        return self._vulnerable(False).filter(is_ghost=False)
 
     def _vulnerable(self, vulnerable=True):
         """