Revert cid changes. (#1029)

* Revert cid changes.

Need to re-think this one.

* generated protobuf

* Create popular-dodos-study.md

---------

Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

Author: boks1971

.changeset/popular-dodos-study.md

@@ -0,0 +1,6 @@
+---
+"github.com/livekit/protocol": patch
+"@livekit/protocol": patch
+---
+
+Revert cid changes.

livekit/livekit_models.pb.go

@@ -196,10 +196,8 @@ message Encryption {
 message SimulcastCodecInfo {
   string mime_type = 1;
   string mid = 2;
-  string signal_cid = 3;
+  string cid = 3;
   repeated VideoLayer layers = 4;
-  string sdp_cid = 5;
-  bool is_simulcast = 6;
 }
 
 message TrackInfo {