obs-ffmpeg: Update error message in process_packet

The error message in the process_packet function was prefixed with
"receive_audio" because it was previously from code in the encode_audio
function which was called from the receive_audio function. This is just
a string change to avoid being misled to believe that the error is
always audio related.

plugins/obs-ffmpeg/obs-ffmpeg-output.c

@@ -952,7 +952,7 @@ static int process_packet(struct ffmpeg_output *output)
 	if (ret < 0) {
 		av_free_packet(&packet);
 		ffmpeg_log_error(LOG_WARNING, &output->ff_data,
-				 "receive_audio: Error writing packet: %s",
+				 "process_packet: Error writing packet: %s",
 				 av_err2str(ret));
 		return ret;
 	}