voice: use getters where possible

src/client/voice/VoiceConnection.js

@@ -36,12 +36,6 @@ class VoiceConnection extends EventEmitter {
      */
     this.voiceManager = voiceManager;
 
-    /**
-     * The client that instantiated this connection
-     * @type {Client}
-     */
-    this.client = voiceManager.client;
-
     /**
      * The voice channel this connection is currently serving
      * @type {VoiceChannel}
@@ -116,6 +110,14 @@ class VoiceConnection extends EventEmitter {
     this.authenticate();
   }
 
+  /**
+   * The client that instantiated this connection
+   * @type {Client}
+   */
+  get client() {
+    return this.voiceManager.client;
+  }
+
   /**
    * The current stream dispatcher (if any)
    * @type {?StreamDispatcher}