fix: torchtune precalculate_logprobs

Author: bradhilton

src/art/torchtune/recipe.py

@@ -860,7 +860,7 @@ def explain_block_diffs(
         del hidden_states, logits
 
         if return_new_logprobs:
-            return torch.nn.functional.pad(new_logprobs[:, :-1], (1, 0), value=0.0)
+            return torch.nn.functional.pad(new_logprobs[:-1], (1, 0), value=0.0)
 
         old_logprobs = torch.where(
             torch.isnan(old_logprobs),