Remove installation of schema_triggers

Schema triggers dependency was deprecated time ago. See
https://github.com/CartoDB/cartodb-postgresql/blob/5d43faecaf5659cbc32f3e9468e10e029ea47cd7/NEWS.md#0120-2016-01-27

client/test/sql/00_installation_test.sql

@@ -1,6 +1,5 @@
 -- Install dependencies
 CREATE EXTENSION postgis;
-CREATE EXTENSION schema_triggers;
 CREATE EXTENSION plpythonu;
 CREATE EXTENSION cartodb;
 CREATE EXTENSION plproxy;