malaria_vaccdrug_campaigns problem 2/2 make_drug_vehicle()

[tobias-holden]

Discussed w Svetlana:
Error when calling add_vaccdrug_smc() because make_vehicle_drug is not callable from inside a campaign-creating function.

(see here: https://github.com/InstituteforDiseaseModeling/emodpy-snt/blob/main/snt/support_files/malaria_vaccdrug_campaigns.py#L183-L194)

[stitova-idm]

this makes the code as-is unusable :( big bug