Update URI of TransportSequenceNumberV2

The previous URI was a placeholder and is not valid. The URI
https://webrtc.org/experiments/rtp-hdrext/transport-wide-cc-02/
must be used instead.

Bug: webrtc:10264
Change-Id: Ibabde599b5bbd116c1c5e86ba0c9c64019bf7026
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/126360
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Johannes Kron <kron@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27051}
diff --git a/pc/media_session_unittest.cc b/pc/media_session_unittest.cc
index e876c36..7c0a7de 100644
--- a/pc/media_session_unittest.cc
+++ b/pc/media_session_unittest.cc
@@ -223,15 +223,15 @@
     RtpExtension("http://www.ietf.org/id/"
                  "draft-holmer-rmcat-transport-wide-cc-extensions-01",
                  1),
-    RtpExtension("http://www.ietf.org/id/"
-                 "draft-holmer-rmcat-transport-wide-cc-extensions-02",
-                 2),
+    RtpExtension(
+        "http://www.webrtc.org/experiments/rtp-hdrext/transport-wide-cc-02",
+        2),
 };
 
 static const RtpExtension kRtpExtensionTransportSequenceNumber02[] = {
-    RtpExtension("http://www.ietf.org/id/"
-                 "draft-holmer-rmcat-transport-wide-cc-extensions-02",
-                 2),
+    RtpExtension(
+        "http://www.webrtc.org/experiments/rtp-hdrext/transport-wide-cc-02",
+        2),
 };
 
 static const uint32_t kSimulcastParamsSsrc[] = {10, 11, 20, 21, 30, 31};