remove some dead code

Related to an earlier failed attempt of reconciling CallKit audio
management with WebRTC's.

// FREEBIE

Signal/src/call/PeerConnectionClient.swift

@@ -275,25 +275,6 @@ class PeerConnectionClient: NSObject {
         let buffer = RTCDataBuffer(data: data, isBinary: false)
         return dataChannel.sendData(buffer)
     }
-
-    // MARK: CallAudioManager
-
-    internal func configureAudioSession() {
-        Logger.warn("TODO: \(#function)")
-    }
-
-    internal func stopAudio() {
-        Logger.warn("TODO: \(#function)")
-    }
-
-    internal func startAudio() {
-        guard let audioSender = self.audioSender else {
-            Logger.error("\(TAG) ignoring \(#function) because audioSender was nil")
-            return
-        }
-
-        Logger.warn("TODO: \(#function)")
-    }
 }
 
 /**