Change example value sets for MS items to Preferred - Immunization-related

ImmunizationEvaluation contains 3 example value sets for Must Support elements:

• ImmunizationEvaluation.doseStatus using http://hl7.org/fhir/ValueSet/immunization-evaluation-dose-status
• ImmunizationEvaluation.doseStatusReason using http://hl7.org/fhir/ValueSet/immunization-evaluation-dose-status
• For these two items, the value set includes 2 codes: Valid/not-valid - these are used by registries for specific meaning. Might consider "extensible" but "preferred" is better since "preferred" allows other concepts to be included while "extensible" requires use of existing codes even they represent higher level concepts than desired.

and

• ImmunizationEvaluation.targetDisease using http://hl7.org/fhir/ValueSet/immunization-evaluation-target-disease
• Immunization contains 1 example value set for a Must Support element:
  Immunization.statusReason using http://hl7.org/fhir/ValueSet/immunization-status-reason
  This value set is used as a reason not given and these are acceptable terms for a registry. Change to "preferred"