d/control: remove all Pre-Depends

It starts from liblttng-ust having its package name changed again from 64 bit time_t transition, thus preventing liblomirimetrics5t64 from being installed on armhf. But instead of re-rename it again, Mike Gabriel reckons that it should be safe to remove it since we don't actually have a .preinst that requires it. Thus I decided to remove it.

And while we're at it, I figured that Pre-Depends: on dpkg probably isn't needed either, since it has been redundant since Focal. So I think it should be safe to remove that too.

This leaves only ${misc:Pre-Depends} in the list. However, it seems like this variable isn't expanded to anything either. So, at the end, there's no longer any Pre-Depends: in our package, thus it's safe to remove it altogether.