Enable config for fsdp activation checkpointing

[helloworld1]

What does this PR do?

The fsdp_activation_checkpointing config does not currently take effect. The fsdp_plugin still get fsdp_activation_checkpointing = False for the following config

fsdp_config:                                                                                                                        
  fsdp_auto_wrap_policy: TRANSFORMER_BASED_WRAP                                                                                     
  fsdp_backward_prefetch: BACKWARD_PRE                                                                                              
  fsdp_cpu_ram_efficient_loading: true                                                                                              
  fsdp_forward_prefetch: false                                                                                                      
  fsdp_offload_params: false                                                                                                        
  fsdp_sharding_strategy: FULL_SHARD                                                                                                
  fsdp_state_dict_type: SHARDED_STATE_DICT                                                                                          
  sync_module_states: true                                                                                                          
  fsdp_use_orig_params: true                                                                                                        
  fsdp_activation_checkpointing: true     

This PR enables configuration of fsdp_activation_checkpointing

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• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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Who can review?

@pacman100
Anyone in the community is free to review the PR once the tests have passed. Feel free to tag
members/contributors who may be interested in your PR.

[muellerzr]

Thanks!

[muellerzr]

@helloworld1 can you do:

pip install -e .[quality] + make style; make quality?

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[helloworld1]

Fixed! Thanks!