fix: [stix2 export] Exporting TLP tags as marking definition
fix: [stix2 export] Exporting TLP tags as marking definition

- Marking definition in the case of TLP was
  missing and only the reference to the marking
  definition was exported, but not the actual
  marking definition object

MISP/MISP,MISP/MISP,SteveClement/MISP,SteveClement/MISP,SteveClement/MISP,MISP/MISP,SteveClement/MISP,SteveClement/MISP,MISP/MISP,MISP/MISP