Ignore RID that appears without an a=simulcast entry
We should probably cherry-pick https://webrtc-review.googlesource.com/c/src/+/267628
<rdar://problem/96586416>
Pull request: https://github.com/WebKit/WebKit/pull/2164
Committed 252219@main (5db31f51c620): <https://commits.webkit.org/252219@main> Reviewed commits have been landed. Closing PR #2164 and removing active labels.