Do not warn when analysing a typeshed stub file.

Author: tyralla

mypy/checker.py

@@ -7620,7 +7620,7 @@ def warn_deprecated(self, node: SymbolNode | None, context: Context) -> None:
             node = node.func
         if isinstance(node, (FuncDef, OverloadedFuncDef, TypeInfo)) and (
             (deprecated := node.deprecated) is not None
-        ):
+        ) and not self.is_typeshed_stub:
             warn = self.msg.fail if self.options.report_deprecated_as_error else self.msg.note
             warn(deprecated, context, code=codes.DEPRECATED)