style: Remove outdated comments about the use of the former _Paramete…

…r protocol (#3448)

altair/vegalite/v5/api.py

@@ -240,9 +240,6 @@ def _get_channels_mapping() -> dict[type[SchemaBase], str]:
 class Parameter(_expr_core.OperatorMixin):
     """A Parameter object"""
 
-    # NOTE: If you change this class, make sure that the protocol in
-    # altair/vegalite/v5/schema/core.py is updated accordingly if needed.
-
     _counter: int = 0
 
     @classmethod

tools/schemapi/utils.py

@@ -336,11 +336,9 @@ def get_python_type_representation(
                 class_names = ["SchemaBase"]
                 if self.title == "ExprRef":
                     # In these cases, a value parameter is also always accepted.
-                    # We use the _Parameter to indicate this although this
-                    # protocol would also pass for selection parameters but
-                    # due to how the Parameter class is defined, it would be quite
-                    # complex to further differentiate between a value and
-                    # a selection parameter based on the type system (one could
+                    # It would be quite complex to further differentiate
+                    # between a value and a selection parameter based on
+                    # the type system (one could
                     # try to check for the type of the Parameter.param attribute
                     # but then we would need to write some overload signatures for
                     # api.param).