[merge to M104] sdp: temporarily relax channel requirements for statically assigned payload types

to allow for downstream users to upgrade.

BUG=chromium:1338902

(cherry picked from commit c501f30)

No-Try: true
Change-Id: Ie1205ad2c9c1be3f4ed8e133b1a5e54afd04ebd9
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/268193
Commit-Queue: Philipp Hancke <[email protected]>
Reviewed-by: Tomas Gunnarsson <[email protected]>
Cr-Original-Commit-Position: refs/heads/main@{#37501}
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/268469
Commit-Queue: Henrik Boström <[email protected]>
Reviewed-by: Henrik Boström <[email protected]>
Cr-Commit-Position: refs/branch-heads/5112@{#7}
Cr-Branched-From: a976a87-refs/heads/main@{#37168}

Author: fippo

pc/webrtc_sdp.cc

@@ -3633,10 +3633,10 @@ bool ParseRtpmapAttribute(absl::string_view line,
 
     AudioContentDescription* audio_desc = media_desc->as_audio();
     for (const cricket::AudioCodec& existing_codec : audio_desc->codecs()) {
-      // TODO(crbug.com/1338902) re-add check for clockrate.
+      // TODO(crbug.com/1338902) re-add checks for clockrate and number of
+      // channels.
       if (!existing_codec.name.empty() && payload_type == existing_codec.id &&
-          (!absl::EqualsIgnoreCase(encoding_name, existing_codec.name) ||
-           channels != existing_codec.channels)) {
+          (!absl::EqualsIgnoreCase(encoding_name, existing_codec.name))) {
         rtc::StringBuilder description;
         description
             << "Duplicate "