Validation on Gateway MerchantID edit to allow numbers

line 256 preg_match updated to allow numbers preg_match( '/^([a-zA-Z0-9]{6})([-])([0-9]{7})$/'
Merge branch 'patch-1' of https://github.com/PaymentSense-Developer/PrestaShop-modules into PaymentSense-Developer-patch-1
PaymentSense - Version updated (v1.9.6)