Fix ASA: A frozen adventure not working when starting from checkpoint

Remove checkpoints in ASA: Searching in the dust Same rationale as for ASA: Getting to the device

Remove checkpoints in ASA: Getting to the device This means the player now must win this mission in one go. Justification: There were many ways for the mission to be saved in an unwinnable state, there are many ways to win this mission and the checkpoints try to "force" one particular way. Also, this mission isn't too long anyway.