Translate "Fields marked with an * are required"

i18n_front_end.php

<?php

add_filter( 'ninja_forms_i18n_front_end', 'my_custom_ninja_forms_i18n_front_end' );
function my_custom_ninja_forms_i18n_front_end( $strings ) {
    $strings['fieldsMarkedRequired'] = 'Polja označena * su obavezna';
    return $strings;
}