sfx2: remove another DBG macro that arose from the grave

The callers in dispatch.cxx use methods that were removed by commit
a1ce4fb4f0dbc3c4141f510e5b2b732a24d862c8 - not sure if this warning is
useful or not.

Change-Id: I8bb654de8e26c054318dd2037055a85d013c8bfa