Rename deprecated argument (temporal_ensemble_momentum)

[KasparSLT]

What this does

Title	Label
Fixes #[issue]	(🐛 Bug)

Renamed deprecated argument in Hydra config files to match torch implementation.
Should have been fixed here #319 (where act config was changed)

How it was tested

Renamed argument and checked that training converges with policy act_so100_real on own dataset.

How to checkout & try? (for the reviewer)

DATA_DIR=data python lerobot/scripts/train.py \
  dataset_repo_id=${HF_USER}/so100_test \
  policy=act_so100_real \
  env=so100_real \
  hydra.run.dir=outputs/train/act_so100_test \
  hydra.job.name=act_so100_test \
  device=cuda \
  wandb.enable=true

python lerobot/scripts/control_robot.py record \
  --robot-path lerobot/configs/robot/so100.yaml \
  --fps 30 \
  --root data \
  --repo-id ${HF_USER}/eval_act_so100_test \
  --tags so100 tutorial eval \
  --warmup-time-s 5 \
  --episode-time-s 40 \
  --reset-time-s 10 \
  --num-episodes 10 \
  -p outputs/train/act_so100_test/checkpoints/last/pretrained_model