Change SNOMED direct-reference code to version-less

[brynrhodes]

Best practices for direct-reference codes are that version-less references should be used (unless there is a specific need to reference a particular code system version). Suggest that the following version-specific references to code systems be converted to version-independent references:

https://github.com/cqframework/draft-measures/blob/master/pages/cql/complete/fhir3/EXM124_FHIR3-7.2.000.cql#L37

https://github.com/cqframework/draft-measures/blob/master/pages/cql/complete/fhir3/Hospice_FHIR3-1.0.000.cql#L20

https://github.com/cqframework/draft-measures/blob/master/pages/cql/complete/fhir3/Hospice_FHIR3-1.0.000.cql

https://github.com/cqframework/draft-measures/blob/master/pages/cql/complete/fhir3/VTEICU_FHIR3-2.4.000.cql#L21