Optimizes training progress bar

[harshav17]

What this does

Previously progress bar was hard to read. This PR tries to make the PR more visually appealing.

How it was tested

Manually by running the train.py script

python lerobot/scripts/train.py   --policy.path=lerobot/smolvla_base   --dataset.repo_id=harshav17/salt-test   --batch_size=48   --steps=20000   --output_dir=outputs/train/my_smolvla   --job_name=my_smolvla_training   --policy.device=cuda   --wandb.enable=true

How to checkout & try? (for the reviewer)

Simply run the following script to train smolvla_base model.

python lerobot/scripts/train.py   --policy.path=lerobot/smolvla_base   --dataset.repo_id=harshav17/salt-test   --batch_size=48   --steps=20000   --output_dir=outputs/train/my_smolvla   --job_name=my_smolvla_training   --policy.device=cuda   --wandb.enable=true

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