Change default conf for MIDI beat clock to disabled

Wastes CPU time on extra timing if not needed, and is probably undesired
by default, since it may interfere with sequencers.

tui_main.c

@@ -939,7 +939,7 @@ static void ged_init(Ged *a, Usz undo_limit, Usz init_bpm, Usz init_seed) {
   a->needs_remarking = true;
   a->is_draw_dirty = false;
   a->is_playing = false;
-  a->midi_bclock = true;
+  a->midi_bclock = false;
   a->draw_event_list = false;
   a->is_mouse_down = false;
   a->is_mouse_dragging = false;