pythongh-119562: Remove unused private string constants from ast.py (python#119576)

Author: AlexWaygood

Lib/ast.py

@@ -567,15 +567,6 @@ def generic_visit(self, node):
                     setattr(node, field, new_node)
         return node
 
-
-_DEPRECATED_VALUE_ALIAS_MESSAGE = (
-    "{name} is deprecated and will be removed in Python {remove}; use value instead"
-)
-_DEPRECATED_CLASS_MESSAGE = (
-    "{name} is deprecated and will be removed in Python {remove}; "
-    "use ast.Constant instead"
-)
-
 class slice(AST):
     """Deprecated AST node class."""