Revert "avcodec/gsmdec: reject unsupported msn audio modes"

they should be supported now

This reverts commit 1ee1a3d9.

libavcodec/gsmdec.c

@@ -34,14 +34,6 @@
 
 static av_cold int gsm_init(AVCodecContext *avctx)
 {
-    if (avctx->codec_tag == 0x0032 &&
-        avctx->bit_rate != 13000 &&
-        avctx->bit_rate != 17912 &&
-        avctx->bit_rate != 35824 &&
-        avctx->bit_rate != 71656) {
-        av_log(avctx, AV_LOG_ERROR, "Unsupported audio mode\n");
-        return AVERROR_PATCHWELCOME;
-    }
     avctx->channels       = 1;
     avctx->channel_layout = AV_CH_LAYOUT_MONO;
     if (!avctx->sample_rate)