change "actions_id_pad" to "actions_is_pad"(🐛 Bug) (huggingface#774)

Co-authored-by: Steven Palma <[email protected]>

Author: yachenkang

lerobot/common/policies/pi0/modeling_pi0.py

@@ -313,7 +313,7 @@ def forward(self, batch: dict[str, Tensor], noise=None, time=None) -> tuple[Tens
         state = self.prepare_state(batch)
         lang_tokens, lang_masks = self.prepare_language(batch)
         actions = self.prepare_action(batch)
-        actions_is_pad = batch.get("actions_id_pad")
+        actions_is_pad = batch.get("actions_is_pad")
 
         loss_dict = {}
         losses = self.model.forward(images, img_masks, lang_tokens, lang_masks, state, actions, noise, time)