Revert "wireguard: prefer wireguard-modules (from a kernel package) over wireguard-dkms"

This reverts commit 2d363650.

Ubuntu keeps screwing up the Provides: on their kernel packages, over and over and over again, causing incredible breakage for their users, when installing WireGuard tries to pull in a Google Cloud Computing kernel to satisfy the "Depends: wireguard-modules" on a laptop. This has caused huge problems and broken people's computers.

Obviously the correct fix for them is to add the "Provides: wireguard-module" in the places where they've forgotten to add it. But it seems like instead they're prioritizing bandaiding it by reversing the order of the Depends, which is what this revert commit does too.

So while Ubuntu is obviously solving the wrong problem here, I still wonder if we too should consider reversing the order of the Depends:. We had a justification when we first did it this way. Does it still apply? Or is it time to change?

I'm not squarely decided, but I thought I'd post this commit for discussion.