SendGrid response code ignored due to typo

At the end of SendGridMailSystem->send() we have:

    if ($response_code = 200) {
      // If the code is 200 we are good to finish and proceed.
      return TRUE;
    }
    // Default to low. Sending failed.
    return FALSE;

We need:

    if ($response_code == 200) {
      // If the code is 200 we are good to finish and proceed.
      return TRUE;
    }
    // Default to low. Sending failed.
    return FALSE;