adjust type hint for Symfony 6

[araab]

related to bshaffer/oauth2-server-httpfoundation-bridge#42

fixes the following errors:

Declaration of OAuth2\HttpFoundationBridge\Response::setStatusCode(int $statusCode, ?string $text = null): static must be compatible with OAuth2\ResponseInterface::setStatusCode($statusCode)
public function setStatusCode(int $statusCode); in ResponseInterface and OAuth\Response.php 

[bshaffer]

Tests passed in #1034 (not sure why they didn't run here)

Thanks for this!

[bshaffer]

We've released v1.7, so this should now be resolved! Thanks for submitting those!