Cleanup RtpHeaderExtensionMap removing use of two legacy functions

webrtc/modules/rtp_rtcp/source/rtp_header_extension.h

Index: webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h b/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
index 1ec411dbcc55bed09e0213fbc4f682bce84e8477..777155b3a6bb4a13ab0c700d75b3b9a39101f1c9 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
+++ b/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
@@ -77,11 +77,6 @@ class RtpHeaderExtensionMap {
     return RegisterByType(id, type) ? 0 : -1;
   }
   int32_t Deregister(RTPExtensionType type);
-  int32_t GetType(uint8_t id, RTPExtensionType* type) const {
-    *type = GetType(id);
-    return *type == kInvalidType ? -1 : 0;
-  }
-  void GetCopy(RtpHeaderExtensionMap* copy) const { *copy = *this; }
 
  private:
   static constexpr uint8_t kMinId = 1;