Delete RtpHeaderExtensionMap::Register deprecated long time ago

Bug: None
Change-Id: I2c3d1243bdfc7c9b6c4cdd326454b5b07ed0dde5
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/177842
Commit-Queue: Markus Handell <handellm@webrtc.org>
Reviewed-by: Markus Handell <handellm@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31552}

modules/rtp_rtcp/include/rtp_header_extension_map.h

@@ -51,10 +51,6 @@ class RtpHeaderExtensionMap {
     return ids_[type];
   }
 
-  // TODO(danilchap): Remove use of the functions below.
-  RTC_DEPRECATED int32_t Register(RTPExtensionType type, int id) {
-    return RegisterByType(id, type) ? 0 : -1;
-  }
   int32_t Deregister(RTPExtensionType type);
   void Deregister(absl::string_view uri);