fix(destination): avoid blocking in synchronizedGetStream.Stop (#14621)

synchronizedGetStream.Stop incorrectly tried to send on an unbuffered channel.
Now it closes the channel to avoid blocking.

Author: olix0r

controller/api/destination/syncronized_get_stream.go

@@ -71,5 +71,5 @@ func (s *synchronizedGetStream) Start() {
 }
 
 func (s *synchronizedGetStream) Stop() {
-	s.done <- struct{}{}
+	close(s.done)
 }