UI: Use flac for lossless audio

It was mistakenly using ac3 at a high bitrate -- lossless should be
lossless, both video and audio.

obs/window-basic-main-outputs.cpp

@@ -153,10 +153,9 @@ void SimpleOutput::LoadRecordingPreset_Lossless()
 	obs_output_release(fileOutput);
 
 	obs_data_t *settings = obs_data_create();
-	obs_data_set_string(settings, "format_name", "avi");
+	obs_data_set_string(settings, "format_name", "mkv");
 	obs_data_set_string(settings, "video_encoder", "utvideo");
-	obs_data_set_int(settings, "audio_bitrate", 512);
-	obs_data_set_string(settings, "audio_encoder", "ac3");
+	obs_data_set_string(settings, "audio_encoder", "flac");
 
 	obs_output_update(fileOutput, settings);
 	obs_data_release(settings);
@@ -451,7 +450,7 @@ bool SimpleOutput::StartRecording()
 	if (lastChar != '/' && lastChar != '\\')
 		strPath += "/";
 
-	strPath += GenerateTimeDateFilename(ffmpegOutput ? "avi" : format,
+	strPath += GenerateTimeDateFilename(ffmpegOutput ? "mkv" : format,
 			noSpace);
 
 	SetupOutputs();