fix: [stix2 import] Fixed relationships parsing
fix: [stix2 import] Fixed relationships parsing

- Using iterators is good for a single iteration,
  but not for more, including an if test
- Using tuples instead is better and avoids then
  losing our relationships

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