fix executable batch size issue
# What does this PR do?
1. Fixes #24050 
2. Context: We weren't handling properly the `auto_find_batch_size=True` case. Here, we need to free all of the stored model references in the Accelerator each time as mentioned in the https://github.com/huggingface/accelerate/blob/main/examples/by_feature/automatic_gradient_accumulation.py
3. This PR does that.

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