Revert "obs-ffmpeg: Use FFmpeg's "fast" AAC encoder by default"

This reverts commit aa58b9cf5f.

FFmpeg has reverted their default AAC encoder from fast to twoloop,
which has much better rate control management, making it closer to CBR,
and it sounds much better.

plugins/obs-ffmpeg/obs-ffmpeg-audio-encoders.c

@@ -22,7 +22,6 @@
 #include <obs-module.h>
 
 #include <libavutil/channel_layout.h>
-#include <libavutil/opt.h>
 #include <libavformat/avformat.h>
 
 #include "obs-ffmpeg-formats.h"
@@ -265,7 +264,6 @@ static void *enc_create(obs_data_t *settings, obs_encoder_t *encoder,
 	}
 
 	if (strcmp(enc->codec->name, "aac") == 0) {
-		av_opt_set(enc->context->priv_data, "aac_coder", "fast", 0);
 	}
 
 #if LIBAVCODEC_VERSION_INT < AV_VERSION_INT(59, 24, 100)