Update btrisolve docs to the newest interface.

Author: bamos

torch/_torch_docs.py

@@ -4438,8 +4438,8 @@
 
  >>> A = torch.randn(2, 3, 3)
  >>> b = torch.randn(2, 3)
- >>> A_LU_data, A_LU_pivots, info = torch.btrifact(A)
- >>> x = b.trisolve(A_LU_data, A_LU_pivots)
+ >>> A_LU = torch.btrifact(A)
+ >>> x = b.btrisolve(*A_LU)
  >>> torch.norm(A.bmm(x.unsqueeze(2)) - b)
  6.664001874625056e-08