Typo fix

Author: fre5h

src/JsonSchema/Validator.php

@@ -30,7 +30,7 @@ class Validator extends BaseConstraint
      * Both the php object and the schema are supposed to be a result of a json_decode call.
      * The validation works as defined by the schema proposal in http://json-schema.org.
      *
-     * Note that the first argument is passwd by reference, so you must pass in a variable.
+     * Note that the first argument is passed by reference, so you must pass in a variable.
      *
      * {@inheritdoc}
      */