更新 'PC端在线支付接入规范文档.md'

PC端在线支付接入规范文档.md

@@ -661,7 +661,7 @@ American Express:
 cardNo: 375532604034750 
 expirationMonth: 06 
 expirationYear: 28
-cvv: 6688
+cvv: 688
 firstName: Ken 
 lastName: Swift