Update etl diagram for poi layer (#1297)

Add the missing `osm_poi_stop_centroid` and `osm_poi_stop_rank` materialized views.

layers/poi/poi_stop_agg.sql

@@ -1,3 +1,4 @@
+-- etldoc:  osm_poi_point ->  osm_poi_stop_centroid
 DROP MATERIALIZED VIEW IF EXISTS osm_poi_stop_centroid CASCADE;
 CREATE MATERIALIZED VIEW osm_poi_stop_centroid AS
 (
@@ -11,6 +12,8 @@ GROUP BY uic_ref
 HAVING count(*) > 1
     ) /* DELAY_MATERIALIZED_VIEW_CREATION */;
 
+-- etldoc:  osm_poi_stop_centroid ->  osm_poi_stop_rank
+-- etldoc:  osm_poi_point ->  osm_poi_stop_rank
 DROP MATERIALIZED VIEW IF EXISTS osm_poi_stop_rank CASCADE;
 CREATE MATERIALIZED VIEW osm_poi_stop_rank AS
 (

layers/poi/update_poi_point.sql

@@ -25,6 +25,7 @@ $$ LANGUAGE plpgsql;
 
 SELECT update_osm_poi_point();
 
+-- etldoc:  osm_poi_stop_rank ->  osm_poi_point
 CREATE OR REPLACE FUNCTION update_osm_poi_point_agg() RETURNS void AS
 $$
 BEGIN