message: Fixed: remove a useless attribute.
diff: dmc-datepicker.Datepicker
  .Datepicker__label(if="{ !!opts.label }") { opts.label }
  - form.Datepicker__form(ref="form" onSubmit="{ handleFormSubmit }")
  + form.Datepicker__form(onSubmit="{ handleFormSubmit }")
  input.Datepicker__input(onTap="handleTap" ref="touch" value="{ opts.date }" placeholder="{ opts.placeholder || '' }" readonly="readonly" onInput="{ handleInputInput }" onChange="{ handleInputChange }")
  .Datepicker__calendar(if="{ opts.isshown }")
  .Datepicker__head
  