Synthetic data generation for OMOP isn't quite right.

[EthanSteinberg]

The OMOP tutorial https://github.com/som-shahlab/femr/blob/main/tutorials/2a_OMOP_ETL.ipynb doesn't currently run because the synthetic data generator isn't creating the required "value_as_concept_id" column

See https://github.com/som-shahlab/femr/blob/main/tutorials/synthetic_data_generation/generate_omop.py