text: Title: [Proposal] Allow frame stack for stacks of size 1
  Body: ### Proposal
  
  Hi,
  
  I propose that the framework is updated to allow frame stacks of size 1. This could be helpful for pipelines which might use frame stacks in some settings and omit them in others. By allowing frame stacks of size 1 the frame stack wrapper can be left in the code and automatically add the extra dimension for frame stacking.
  
  To implement this, simply remove these lines:
  https://github.com/Farama-Foundation/Gymnasium/blob/a4f1a93dc19261049b352d45427c260ecab0f0a7/gymnasium/wrappers/stateful_observation.py#L377-L380
  
  Previous versions of the gym wrapper supported this: https://github.com/openai/gym/blob/master/gym/wrappers/frame_stack.py
  
  ### Motivation
  
  As described above, this will enable cleaner code for several applications without causing any issues to existing ones. Also, this is consistent with previous versions of the gym frame stack wrapper.
  
  ### Pitch
  
  Just remove these lines or maybe assert stack-size > 0 instead
  
   https://github.com/Farama-Foundation/Gymnasium/blob/main/gymnasium/wrappers/stateful_observation.py#L377-L380
  
  ### Alternatives
  
  _No response_
  
  ### Additional context
  
  _No response_
  
  ### Checklist
  
  - [X] I have checked that there is no similar [issue](https://github.com/Farama-Foundation/Gymnasium/issues) in the repo
  