Remove Identical validator type hint

7bcd59a8 introduced an array type hint for the `$context` parameter in `Zend\Validator\Identical::isValid()`. This causes PHP errors if the InputFilter containing the Identical validator is executed on form values (they are passed not as arrays, but `Zend\Stdlib\Parameters`).

Remove the type hint and add a check if `$context` is `array` or `ArrayObject`.