Remove warnings (#111)

- Replace `use_pretrained_backbone` with `pretrained_backbone_weights`
- Bump diffusers' minimum version `0.26.3` -> `0.27.2`
- Add ignore flags in CI's pytest
- Change Box observation spaces in simulation environments
- Set `version_base="1.2"` in Hydra initializations
- Bump einops' minimum version `0.7.0` -> `0.8.0`

lerobot/configs/policy/act.yaml

@@ -45,7 +45,7 @@ policy:
   # Architecture.
   # Vision backbone.
   vision_backbone: resnet18
-  use_pretrained_backbone: true
+  pretrained_backbone_weights: ResNet18_Weights.IMAGENET1K_V1
   replace_final_stride_with_dilation: false
   # Transformer layers.
   pre_norm: false