Changes to Update an instance group

the description request property type changed from string to object

the template/allOf[#/components/schemas/MutableInstanceGroupTemplateDto]/startup_script_id request property type changed from string to object

the deleted_at response's property type changed from string to object, and format from date-time to no format for status 200

the description response's property type changed from string to object for status 200

added the required property instances to the response with the 200 status

added the required property size to the response with the 200 status

endpoint added