Bump readme notes

Author: SecondeJK

README.md

@@ -8,10 +8,9 @@ Client Library for PHP
 
 ![The Vonage logo](./vonage_logo.png)
 
-*This library requires a minimum PHP version of 7.4*
+*This library requires a minimum PHP version of 8.0*
 
-This is the PHP client library for use Vonage's API. To use this, you'll need a Vonage account. Sign up [for free at 
-nexmo.com][signup].
+This is the PHP client library for use Vonage's API. To use this, you'll need a Vonage account. [Sign up for free here](https://ui.idp.vonage.com/ui/auth/registration).
 
  * [Installation](#installation)
  * [Usage](#usage)