Which makes absolutely no sense whatsoever.
Galactus devours entire planets. He can wipe out entire star systems with a thought. He is equal in power to the physical embodiments of Death, Infinity, Eternity and Oblivion in the Marvel universe. He's essentially a living, thinking, doing-whatever-the-fuck-he-wants weaponized universal constant. He is not something that you can destroy with lasers or subvert with nanomachines. If you want to take him out, you either need to be able to warp the fabric of reality on a multiversal scale or have ridiculously high-end magic (which, in effect, is no different from the former), two things that the Borg do not have.
The Borg, by comparison, are ants. In fact, even that's being generous. They control, what, a fourth of a galaxy? Even less than that, I think. Galactus wouldn't even be inconvenienced by them; he could just turn them into slime with a thought. Worst comes to worst? Use the Ultimate Nullifier on them. What is the Ultimate Nullifier, you ask? It destroys everything and anything you want it to, as long as you know what it is. You don't like the color blue? Fuck blue! It's been nullified. The Borg are fucking with you? Not anymore!
Someone can draw a picture of the Borg somehow managing to assimilate Galactus, even though it makes absolutely no fucking sense whatsoever, sure. I can also draw a picture of a five year old with polio taking down the Hulk, it doesn't prove anything.
P.S. If you beat Galactus, then Abraxas comes out and destroys the multiverse, so even if the Borg beat him they'd still get fucked over.