message: Delete RtpHeaderExtensionMap::Register deprecated long time ago
  Cr-Commit-Position: refs/heads/master@{#31552}
diff: @@ -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);
  