[Cache] Updated invalid pdo service name

Nyholm · Nyholm · commit fbb3432e6c3f · 2019-04-08T20:41:42.000+02:00
diff --git a/reference/configuration/framework.rst b/reference/configuration/framework.rst
@@ -2016,7 +2016,8 @@ default_pdo_provider
 **type**: ``string`` **default**: ``doctrine.dbal.default_connection``
 
 The service id of the database connection, which should be either a PDO or a
-Doctrine DBAL instance.
+Doctrine DBAL instance. The provider is available as the ``cache.default_pdo_provider``
+service.
 
 pools
 .....
