Fix @return value ?RetailerTimeSlotInterface and not array

[aurelien-andre]

https://github.com/Smile-SA/magento2-module-store-locator/blob/14655c0bd95ba360716205505efc8e94d743b4d8/Model/Retailer/ScheduleManagement.php#L57

If a TimeSloteInterface is found, return that interface and not an array.

Change

/**
 * Retrieve opening hours for a given date
 *
 * @SuppressWarnings(PHPMD.StaticAccess)
 *
 * @param RetailerInterface $retailer The retailer
 * @param null              $dateTime The date to retrieve opening hours for
 *
 * @return RetailerTimeSlotInterface|null
 */
public function getOpeningHours($retailer, $dateTime = null): ?RetailerTimeSlotInterface
{
    $dayOpening = null;

    if ($dateTime == null) {
        $dateTime = new \DateTime();
    }
    if (is_string($dateTime)) {
        $dateTime = \DateTime::createFromFormat('Y-m-d', $dateTime);
    }

    $dayOfWeek = $dateTime->format('w');
    $date      = $dateTime->format('Y-m-d');

    $openingHours = $retailer->getExtensionAttributes()->getOpeningHours();
    $specialOpeningHours = $retailer->getExtensionAttributes()->getSpecialOpeningHours();

    if (isset($openingHours[$dayOfWeek])) {
        $dayOpening = $openingHours[$dayOfWeek];
    }

    if (isset($specialOpeningHours[$date])) {
        $dayOpening = $specialOpeningHours[$date];
    }

    return $dayOpening;
}