[Cache] Add note that Predis ignores the auth option

Author: wikando-ck

components/cache/adapters/redis_adapter.rst

@@ -189,6 +189,11 @@ Available Options
     for ACL-based authentication. When ``null``, the credentials are extracted from
     the DSN (e.g. ``redis://user:password@host``).
 
+    .. note::
+
+        When using `Predis`_, this option is ignored. Provide credentials via the
+        DSN instead.
+
 ``persistent`` (type: ``int``, default: ``0``)
     Enables or disables use of persistent connections. A value of ``0`` disables persistent
     connections, and a value of ``1`` enables them.