logind: remove warn_melody() logic

The internal speaker is usually not available on modern latops that
support suspend, and even if it is available in the hardware, most
distributions turned support for it off in the kernel. And even if it is
enabled, it's probably still a bad idea to make use of it for the
suspend-failures. If anything a proper sound should be played.

Long story short, let's remove support of this anachronism.