Make ConnectionError.Failed not log.

[ByThePowerOfScience]

I'm guessing the real reason for this issue happening now is that Discord still has an IPC file despite not running. However, since there's no non-brittle way to know if Discord is actually running, and KDiscordIPC doesn't let us know why the connection failed, I figure the next best thing is just to not make the user know about it.

The drawback is that if there's an actual problem preventing the rich presence from activating, the only way to know is to let the user discover it themselves by looking at their Discord instance.

Fixes #396 by hiding it. Not my favorite solution, but it's not reporting a problem to begin with.