message: Fix rendering of SelectionOrder docs
  Summary: T14179
  Test Plan: Look at the docs
  Reviewers: #tensorflow, georgep
diff: @@ -49,6 +49,9 @@ class SelectionOrder(Enum):
  return o3
  and a typical machine with 8 Graphcore C2 cards:
  +
  + .. code-block:: none
  +
  _______ _______
  | | | |
  | 14 |=============| 15 |
  