Make k_sneakertimer no longer hold acceleration input

This MR makes it so that when you use sneakers or panels, the acceleration input is no longer held down. This isn't necessary since it's the forward move that actually moves you forward, not the acceleration input itself. This should also serve as a fix for Lua scripts that require players to press acceleration during gameplay, but can't because due to it being held down by a sneaker or panel (Juicebox tech, for example during boosted spinout).