fix doc

Author: fieyum

README.md

@@ -33,7 +33,6 @@ composer require "kucoin/kucoin-php-sdk:~1.1.0"
 | Environment   | BaseUri                                             |
 |---------------|-----------------------------------------------------|
 | *Production*  | https://api.kucoin.com                              |
-| ~~*Sandbox*~~ | ~~https://openapi-sandbox.kucoin.com~~ (Deprecated) |
 
 ```php
 // Switch to the sandbox environment

src/Api.php

@@ -21,7 +21,7 @@ abstract class Api
     /**
      * @var string SDK update date
      */
-    const UPDATE_DATE = '2024.05.30';
+    const UPDATE_DATE = '2024.05.28';
 
     /**
      * @var string