bugfix: Fix cython stream_event_in to match python impl (#608)

Co-authored-by: William Barnhart <williambbarnhart@gmail.com>

Author: Tim-Thomas

faust/_cython/streams.pyx

@@ -179,8 +179,8 @@ cdef class StreamIterator:
                 self.add_unacked(message)
                 self.on_message_in(tp, offset, message)
 
-                stream_state = self.on_stream_event_in(
-                    tp, offset, self.stream, event)
+            stream_state = self.on_stream_event_in(
+                tp, offset, self.stream, event)
             self.stream._set_current_event(event)
             return (event, event.value, stream_state)
         else: