[Peer Connection] Remove out-dated comment for RTCRtpSender

Delete comment in the IDL for RTCRtpSender which references a bug which
is now closed, making the comment now outdated.

Bug: 700916
Change-Id: I0a1e943a09ea1af6b25e4824979939c234167467
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2077678Reviewed-by: Armando Miraglia <armax@chromium.org>
Reviewed-by: Henrik Boström <hbos@chromium.org>
Commit-Queue: Henrik Boström <hbos@chromium.org>
Commit-Queue: Armando Miraglia <armax@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745001}

third_party/blink/renderer/modules/peerconnection/rtc_rtp_sender.idl

@@ -17,5 +17,4 @@ interface RTCRtpSender {
     [CallWith=ScriptState] Promise<RTCStatsReport> getStats();
     [RuntimeEnabled=RTCInsertableStreams, CallWith=ScriptState, RaisesException] RTCInsertableStreams createEncodedAudioStreams();
     [RuntimeEnabled=RTCInsertableStreams, CallWith=ScriptState, RaisesException] RTCInsertableStreams createEncodedVideoStreams();
-    // TODO(hbos): Implement the rest of RTCRtpSender, https://crbug.com/700916.
 };