fixed typo in demographic description

Author: cgmeyer

gdcdictionary/schemas/demographic.yaml

@@ -8,7 +8,7 @@ category: clinical
 program: '*'
 project: '*'
 description: >
-  Data for the characterization of the patient by means of segementing the population (e.g.,characterization by age, sex, or race).
+  Data for the characterization of the patient by means of segmenting the population (e.g.,characterization by age, sex, or race).
 additionalProperties: false
 submittable: true
 validators: null