please move executable link in APT package from /usr/local/bin/kalk to /usr/bin/kalk

[cerebrate]

(Sorry, I'd have submitted this as a pull request, but I couldn't find the apt packaging files.)

A very minor issue, but APT packaging standards make a point of insisting that packages touch nothing inside the /usr/local/* hierarchy, as that's supposed to be reserved for things the admin installed locally, meaning compiled from source. Having the link in /usr/local/* can confuse some management tools.

(And, after all, as a packaged app, kalk has earned its place in /usr/bin 😁 .)

Thanks!