Delete deprecated PeerConnection methods, and corresponding using declarations.

webrtc/sdk/android/src/jni/peerconnection_jni.cc

Index: webrtc/sdk/android/src/jni/peerconnection_jni.cc
diff --git a/webrtc/sdk/android/src/jni/peerconnection_jni.cc b/webrtc/sdk/android/src/jni/peerconnection_jni.cc
index 11d66b736839693b00ddfea17a2fdb5cfa097ce6..b6a768ef52cd258fd7d487d241c70430bf58d3a7 100644
--- a/webrtc/sdk/android/src/jni/peerconnection_jni.cc
+++ b/webrtc/sdk/android/src/jni/peerconnection_jni.cc
@@ -164,13 +164,6 @@ class ConstraintsWrapper;
 // and dispatches C++ callbacks to Java.
 class PCOJava : public PeerConnectionObserver {
  public:
-  // We need these using declarations because there are two versions of each of
-  // the below methods and we only override one of them.
-  // TODO(deadbeef): Remove once there's only one version of the methods.
-  using PeerConnectionObserver::OnAddStream;
-  using PeerConnectionObserver::OnRemoveStream;
-  using PeerConnectionObserver::OnDataChannel;
-
   PCOJava(JNIEnv* jni, jobject j_observer)
       : j_observer_global_(jni, j_observer),
         j_observer_class_(jni, GetObjectClass(jni, *j_observer_global_)),