fix(overlay): deduplicate secondary subtitle rendering (#208)

src/main/runtime/mpv-client-event-bindings.test.ts

@@ -191,6 +191,8 @@ test('mpv event bindings register all expected events', () => {
     onSubtitleAssChange: () => {},
     onSecondarySubtitleChange: () => {},
     onSubtitleTrackChange: () => {},
+    onSecondarySubtitleTrackChange: () => {},
+    onSecondarySubtitleDelayChange: () => {},
     onSubtitleTrackListChange: () => {},
     onSubtitleTiming: () => {},
     onMediaPathChange: () => {},
@@ -215,6 +217,8 @@ test('mpv event bindings register all expected events', () => {
     'subtitle-ass-change',
     'secondary-subtitle-change',
     'subtitle-track-change',
+    'secondary-subtitle-track-change',
+    'secondary-subtitle-delay-change',
     'subtitle-track-list-change',
     'subtitle-timing',
     'media-path-change',