cleanup(Guild): remove Guild#voice (#5091)

src/structures/Guild.js

@@ -628,15 +628,6 @@ class Guild extends Base {
     );
   }
 
-  /**
-   * The voice state for the client user of this guild, if any
-   * @type {?VoiceState}
-   * @readonly
-   */
-  get voice() {
-    return this.voiceStates.cache.get(this.client.user.id);
-  }
-
   /**
    * Fetches this guild.
    * @returns {Promise<Guild>}