convert checkpoints to safetensors (#5620)

## What type of PR is this? (check all applicable)

- [ ] Refactor
- [ ] Feature
- [x] Bug Fix
- [ ] Optimization
- [ ] Documentation Update
- [ ] Community Node Submission


## Have you discussed this change with the InvokeAI team?
- [x] Yes
- [ ] No, because:

      
## Have you updated all relevant documentation?
- [ ] Yes
- [ ] No


## Description

Seems we elected to convert checkpoints into .bin files when we set it
up. This doesn't seem to corrupt them anymore.

## Related Tickets & Documents

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## Added/updated tests?

- [ ] Yes
- [ ] No : _please replace this line with details on why tests
      have not been included_

## [optional] Are there any post deployment tasks we need to perform?

invokeai/backend/model_management/models/sdxl.py

@@ -141,7 +141,7 @@ class StableDiffusionXLModel(DiffusersModel):
                 version=base_model,
                 model_config=config,
                 output_path=output_path,
-                use_safetensors=False,  # corrupts sdxl models for some reason
+                use_safetensors=True,
                 **kwargs,
             )
         else: