ResearchStudy.Condition: Inconsistencies b/t dbGap, KidsFirst and AnVIL

Not all ResearchStudies have a populated condition

Tests implemented here

test_AggregatedResearchStudy_Condition: AssertionError: 379 of 422 ResearchStudies missing Condition codeable concept
- test_KidsFirstResearchStudy_Condition: AssertionError: 21 of 29 ResearchStudies missing Condition codeable concept
- test_AnvilResearchStudy_Condition: AssertionError: 358 of 393 ResearchStudies missing Condition codeable concept
test_dbGapResearchStudy_Condition: AssertionError: 227 of 1857 ResearchStudies missing Condition codeable concept