Completely revert r2970 as line 84 causes crashes elsewhere. While the rest may not cause any issues it's better to deal with some leaking memory than hard crashes.

Originally committed to SVN as r3042.

aegisub/src/subtitles_provider_libass.cpp

@@ -80,8 +80,6 @@ LibassSubtitlesProvider::LibassSubtitlesProvider() {
 //////////////
 // Destructor
 LibassSubtitlesProvider::~LibassSubtitlesProvider() {
-	ass_free_track(ass_track);
-	ass_renderer_done(ass_renderer);
 }