Update README.markdown

Author: jonnott

README.markdown

@@ -4,7 +4,7 @@
 [![Latest Unstable Version](https://poser.pugx.org/kalnoy/nestedset/v/unstable.svg)](https://packagist.org/packages/kalnoy/nestedset)
 [![License](https://poser.pugx.org/kalnoy/nestedset/license.svg)](https://packagist.org/packages/kalnoy/nestedset)
 
-This is a Laravel 4-12 package for working with trees in relational databases.
+This is a Laravel package for working with trees in relational databases.
 
 *   **Laravel 12.0** is supported since v6.0.??
 *   **Laravel 11.0** is supported since v6.0.4