message: docs: fix traffic splitting layout
diff: Traffic Shifting/Splitting
  ===========================================
  +.. contents::
  + :local:
  +
  Envoy's router can split traffic to a route in a virtual host across
  two or more upstream clusters. There are two common use cases.
  @@ -21,7 +24,7 @@ section describes this scenario in more detail.
  .. _config_http_conn_man_route_table_traffic_splitting_shift:
  Traffic shifting between two upstreams
  -======================================
  +--------------------------------------
  The :ref:`runtime <config_http_conn_man_route_table_route_runtime>` object
  in the route configuration determines the probability of selecting a
  @@ -87,7 +90,7 @@ accomplish the task.
  .. _config_http_conn_man_route_table_traffic_splitting_split:
  Traffic splitting across multiple upstreams
  -===========================================
  +-------------------------------------------
  Consider the ``helloworld`` example again with three versions (v1, v2 and
  v3). Envoy provides two ways to split traffic evenly across the three
  @@ -96,7 +99,7 @@ versions (i.e., ``33%, 33%, 34%``):
  .. _config_http_conn_man_route_table_traffic_splitting_split_percentages:
  (a) Weight-based cluster selection
  -----------------------------------
  +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  The first option is to use a **single** :ref:`route <config_http_conn_man_route_table_route>` with
  :ref:`weighted_clusters <config_http_conn_man_route_table_route_weighted_clusters>`,
  @@ -138,7 +141,7 @@ following runtime variables: ``routing.traffic_split.helloworld.helloworld_v1``,
  .. _config_http_conn_man_route_table_traffic_splitting_split_probabilities:
  (b) Probabilistic route selection
  ----------------------------------
  +^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  The second option is to use **multiple** :ref:`routes <config_http_conn_man_route_table_route>`
  as shown in the traffic shifting example, with :ref:`runtimes <config_http_conn_man_route_table_route_runtime>`
  