Flutter FormBuilderDropdown deprecated field `allowClear: true`

After update Flutter to 3.3.0, parameter allowClear: true is recognised as deprecated:

'allowClear' is deprecated and shouldn't be used. Please use decoration.suffix to set your desired behaviour.
Try replacing the use of the deprecated member with the replacement.

My Widget looks like this:

FormBuilderDropdown(
    onChanged: (value) {
      setState(() {});
    },
    name: 'country',
    decoration: const InputDecoration(
      helperText: 'Country',
    ),
    allowClear: true, // DEPRECATED
    items: items),

What is the simplest way to refactor this?