Remove confusing precision.

doc/extending/using_params.txt

@@ -67,8 +67,7 @@ attribute :attr:`params_type` to an instance of your params Type.
 .. note::
 
    If you want to have multiple parameters you have to bundle those
-   inside a single object and use that as the params type.  Multiple
-   types are not supported.
+   inside a single object and use that as the params type.
 
 For example if we decide to use an int as the params the following
 would be appropriate: