Remove id field from model definition in test

Just making sure this isn’t breaking a test because this isn’t how fields will typically be declared.  They’ll go into the object returned from `instanceDefaults` or into the `setupInstance` method.

Author: marshallswain

test/service-module/model-instance-defaults.test.ts

@@ -38,7 +38,6 @@ function makeContext() {
 
   class Todo extends BaseModel {
     public static modelName = 'Todo'
-    public id
     public description: string
 
     public constructor(data = {}, options?) {