Minor fix in README [skip ci]

Author: shivammathur

README.md

@@ -17,7 +17,7 @@ Following configurations are build nightly.
 ### PHP 8.2.0-dev/master
 [https://github.com/shivammathur/php-builder-windows/releases/tag/php8.2](https://github.com/shivammathur/php-builder-windows/releases/tag/php8.2)
 
-### PHP 8.1.0-dev
+### PHP 8.1.x-dev
 [https://github.com/shivammathur/php-builder-windows/releases/tag/php8.1](https://github.com/shivammathur/php-builder-windows/releases/tag/php8.1)
 
 ### PHP 8.0.x-dev