fix problem doc

Author: GiovanniCanali

pina/problem/zoo/supervised_problem.py

@@ -30,7 +30,7 @@ def __init__(
         Initialization of the :class:`SupervisedProblem` class.
 
         :param input_: Input data of the problem.
-        :type input_: torch.Tensor | LabelTensor | Graph | Data
+        :type input_: torch.Tensor | Graph
         :param output_: Output data of the problem.
         :type output_: torch.Tensor | LabelTensor | Graph | Data
         """