Remove brackets when composing attribute/methods calls

[mathieutu]

-        return $this->quantity * $this->{self::PRICE_ATTRIBUTE};
+        return $this->quantity * $this->self::PRICE_ATTRIBUTE;

[czosel]

Also:

$this->view->bar(
    $this->view->form->{$data['data-some-looooooooooooooooooooong-reference']}->getValue()
);

becomes

$this->view->bar(
    $this->view->form->$data['data-some-looooooooooooooooooooong-reference'
    ]->getValue()
);

[czosel]

Fixed in #183