Cross-language invocation Part 1: Java calling Python functions and actors (#4166)

src/ray/gcs/format/gcs.fbs

@@ -96,8 +96,6 @@ table TaskInfo {
   // uniquely describe a function.
   // For a Python function, it should be: [module_name, class_name, function_name]
   // For a Java function, it should be: [class_name, method_name, type_descriptor]
-  // TODO(hchen): after changing Python worker to use function_descriptor,
-  // function_id can be removed.
   function_descriptor: [string];
 }