Improve PHP 8.2 compatibility - fix Use of "self" in callables is deprecated error

Fixes:

> Deprecated: Use of "self" in callables is deprecated in /../vendor/alcaeus/mongo-php-adapter/lib/Alcaeus/MongoDbAdapter/TypeConverter.php on line 180

Author: spantaleev

lib/Alcaeus/MongoDbAdapter/TypeConverter.php

@@ -178,7 +178,7 @@ private static function convertBSONObjectToLegacy(BSON\Type $value)
             case $value instanceof Model\BSONDocument:
             case $value instanceof Model\BSONArray:
                 return array_map(
-                    ['self', 'toLegacy'],
+                    [__CLASS__, 'toLegacy'],
                     $value->getArrayCopy()
                 );
             default: