[bugfix] Schema reference should be in schema property.

paths/customer_careprogram.yaml

@@ -10,8 +10,9 @@ get:
   parameters:
     - name: refDate
       in: query
-      $ref: ../schemas/date.yaml
       description: If omitted, today is taken.
+      schema:
+        $ref: ../schemas/date.yaml
   responses:
     '200':
       description: All practices for which the care group takes responsibility.