[php] Add `Global.session_destroy()` method (#9827)

Fixes #9826

std/php/Global.hx

@@ -1398,6 +1398,11 @@ extern class Global {
 	**/
 	static function session_cache_expire(?new_cache_expire:Int):Int;
 
+	/**
+		@see http://php.net/manual/en/function.session-destroy.php
+	**/
+	static function session_destroy():Bool;
+
 	/**
 		@see http://php.net/manual/en/function.session-name.php
 	**/