server side cleanup should no longer be necessary w/ new goirc, removing

Signed-off-by: Luca Bigliardi <shammash@google.com>

irc_test.go

@@ -577,9 +577,6 @@ func TestStopRunningWhenHalfConnected(t *testing.T) {
 	cancel()
 	stopWg.Wait()
 
-	// Client has left, cleanup the server side before stopping
-	server.Client.Close()
-
 	server.Stop()
 
 	expectedCommands := []string{