Replace ATC by INN as internal id

Replace ATC by INN(opsMedication.getSubstanzangabeAusOpsCode) here https://gitlab.miracum.org/miracum/etl/p21-to-fhir/-/blob/master/src/main/java/org/miracum/etl/p21tofhir/mappers/OpsMedicationToMedicationMapper.java#L28, https://gitlab.miracum.org/miracum/etl/p21-to-fhir/-/blob/master/src/main/java/org/miracum/etl/p21tofhir/mappers/OpsMedicationToMedicationMapper.java#L31