Disabled bots on maps with separate land masses between destructible bridges

This is a workaround for the problem described at https://github.com/OpenRA/OpenRA/issues/5754 which is also seen in the wild, because newbies tend to like to keep the AI out, build up their base and then wonder for huge path finder lag spikes in the very late game. Essentially the same problem as island maps. https://github.com/OpenRA/OpenRA/issues/2007