fix: keep the behavior of Model casts datetime with timestamp

It returns Time with the default timezone as before.

system/DataCaster/Cast/TimestampCast.php

@@ -32,7 +32,7 @@ public static function get(
             self::invalidTypeValueError($value);
         }
 
-        return Time::createFromTimestamp((int) $value);
+        return Time::createFromTimestamp((int) $value, date_default_timezone_get());
     }
 
     public static function set(