sqv: --output option is mandatory

Was testing the patch that I had prepared to be able to swap «sq verify» for sqv >= 1.3.x in the Dpkg::OpenPGP::Backend::Sequoia, but the tests are failing because sqv requires --output to be passed in contrast to «sq verify». While I need to check whether this is a problem with the dpkg code, and I should always be passing --output, I think the behavior of both tools should be equal.