The default value is multipart/form-data. Use this code example to set it to empty.

add_filter( 'frm_form_enctype', 'custom_form_enctype', 10, 2 );
function custom_form_enctype( $enctype, $form ) {
	$target_form_id = 832; // change 832 to your form ID.
	if ( $target_form_id === (int) $form->id ) {
		$enctype = '';
	}
	return $enctype;
}