Fixed phpstan on Mage_Customer_Model_Customer

[kiatng]

Description (*)

Line 1419 in app\code\core\Mage\Customer\Model\Customer.php

    $region = Mage::getModel('directory/region')->loadByName($data[$prefix . 'region']);

will result in

Fatal error: Uncaught ArgumentCountError: Too few arguments to function Mage_Directory_Model_Region::loadByName()

However, the function validateAddress() is not reference in the core. Removing it is a potential BC, but should we remove it anyway?

[sreichel]

It either should be US or CA, not?

                if ($field == 'country'
                    && in_array(strtolower($data[$prefix . $field]), ['US', 'CA'])
                ) {

I'd not remove any public methods.