sdp: accept bundle-only media section without rtcp-mux

following the example C1 in
https://www.rfc-editor.org/rfc/rfc8829.html#section-7.3
and the rules from
https://www.rfc-editor.org/rfc/rfc8843.html#section-9.3.1.1

BUG=chromium:1444615

Change-Id: I6aedc5a669a9c53b9d65fb564804913203a453f0
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/304980
Reviewed-by: Henrik Boström <hbos@webrtc.org>
Commit-Queue: Philipp Hancke <phancke@microsoft.com>
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#40058}
diff --git a/pc/peer_connection.cc b/pc/peer_connection.cc
index 3f99c96..59d3872 100644
--- a/pc/peer_connection.cc
+++ b/pc/peer_connection.cc
@@ -2570,7 +2570,8 @@
     const cricket::ContentInfo* content = (&*citer);
     RTC_DCHECK(content != NULL);
     auto it = bundle_groups_by_mid.find(content->name);
-    if (it != bundle_groups_by_mid.end() && !content->rejected &&
+    if (it != bundle_groups_by_mid.end() &&
+        !(content->rejected || content->bundle_only) &&
         content->type == MediaProtocolType::kRtp) {
       if (!HasRtcpMuxEnabled(content))
         return false;