Internal variables for generated assert has prefix underscore

[h4kuna]

Bug:

I use interface, where parameter is $message. And internal variable rewrite this parameter.

example

    function captureMessage(string $message, \Sentry\Severity $level = null): ?\Sentry\EventId
    {
        ...
        $message = $this->getDebugMessage(); // <------ Here is rewritten incoming parameter

        Assert::assertEquals($expectation->message, $message, $message);

    }