message: Remove comment referencing deprecated parameter 'global_step'. Instead use `iterations`.
diff: @@ -305,8 +305,8 @@ class OptimizerV2(trackable.Trackable):
  name: Optional name for the returned operation.
  Returns:
  - An Operation that updates the variables in `var_list`. If `global_step`
  - was not `None`, that operation also increments `global_step`.
  + An `Operation` that updates the variables in `var_list`. The `iterations`
  + will be automatically increased by 1.
  Raises:
  ValueError: If some of the variables are not `Variable` objects.
  