libsaria: Remove audio::durstr()

Nothing used it anymore, so it can be removed.

Signed-off-by: Bryan Schumaker <bjschuma@gmail.com>

include/audio.h

@@ -29,7 +29,6 @@ namespace libsaria
 		gint64 duration();
 		gint64 position();
 		string posstr();
-		string durstr();
 		bool played();
 	};
 };

libsaria/audio.cpp

@@ -163,11 +163,6 @@ namespace libsaria
 		return duration;
 	}
 
-	string audio::durstr()
-	{
-		return to_string(duration());
-	}
-
 	gint64 audio::position()
 	{
 		gint64 position;