src/Http/Message.php
public function withoutHeader($header)
    {
        if ($this->hasHeader($header)) {
            $name = strtolower($header);
            unset($this->headers[$name]);
        }

        return $this;
    }
public function withoutHeader($header)
    {
        if ($this->hasHeader($header)) {
            $name = strtolower($header);
            unset($this->headers[$name]);
        }

        return $this;
    }
{@inheritdoc}