remove unused override in the language files

src/main/resources/assets/playersync/lang/en_us.json

@@ -1,6 +1,5 @@
 {
   "playersync.item_placeholder_description": "Item is unknown on this server. This can either\nbe a modded item, an added, or a removed vanilla\nitem.\nThis voucher will automatically be replaced with\nthe corresponding item when joining a server\nwhere the item is known.",
-  "playersync.placeholder_title_override": "Item Voucher",
   "playersync.item_placeholder_title": "Item Voucher",
   "playersync.already_online": "You can't join more than one synchronization server at the same time."
 }

src/main/resources/assets/playersync/lang/zh_cn.json

@@ -1,6 +1,5 @@
 {
   "playersync.item_placeholder_description": "物品在此服务器未知。这可能是一个模组物品,或是不同版本的原版物品。\n这张券将会在加入可识别此物品的服务器后自动替换为对应物品。",
-  "playersync.placeholder_title_override": "物品券",
   "playersync.item_placeholder_title": "物品券",
   "playersync.already_online": "你不能同时加入多个同步的服务器。"
-}
+}