Deduplicate set of the rtp header extension uri constants

Bug: webrtc:7472
Change-Id: Ic0b4f2cc3374ba70a043310b5046d8bf91f0acbe
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/231949
Reviewed-by: Tommi <tommi@webrtc.org>
Commit-Queue: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#34990}
diff --git a/api/rtp_parameters.cc b/api/rtp_parameters.cc
index 5ce6780..308fe72 100644
--- a/api/rtp_parameters.cc
+++ b/api/rtp_parameters.cc
@@ -131,6 +131,7 @@
 constexpr char RtpExtension::kRidUri[];
 constexpr char RtpExtension::kRepairedRidUri[];
 constexpr char RtpExtension::kVideoFrameTrackingIdUri[];
+constexpr char RtpExtension::kCsrcAudioLevelsUri[];
 
 constexpr int RtpExtension::kMinId;
 constexpr int RtpExtension::kMaxId;