Bring Flamethrower speed back up to 4.5

Flamethrowers were modified in playtest, and slowed down from speed 5 -> 4.
This seemed reasonable since they are super powerful. However, the lowered speed allows them to be kited by minigunners.
Also, it presents the problem that Nod no longer has any fast infantry, which is a bit of a pain against some units.
I wanted the flamers to be powerful more than fast, and it seemed having them be both was OP. However, after some testing it seems like it would be better to give them some speed. After playing a few test games, I'm hoping 4.5 will be enough.