rtsp: Remove an outdated comment

It is unclear what the bug exactly was and if it ever was fixed,
and we don't even support decoding via faad any longer. The
comment has been present since d0deedcb in 2006.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/rtsp.c

@@ -243,10 +243,6 @@ static int sdp_parse_rtpmap(AVFormatContext *s,
             i = atoi(buf);
             if (i > 0)
                 codec->channels = i;
-            // TODO: there is a bug here; if it is a mono stream, and
-            // less than 22000Hz, faad upconverts to stereo and twice
-            // the frequency.  No problem, but the sample rate is being
-            // set here by the sdp line. Patch on its way. (rdm)
         }
         av_log(s, AV_LOG_DEBUG, "audio samplerate set to: %i\n",
                codec->sample_rate);