fix: 修复 Bot#getPrivateChat 接口请求体格式错误 (#53)

Author: kaikaibenkai

src/bot.ts

@@ -615,7 +615,7 @@ export class Bot {
    */
   public async getPrivateChat(user: bigint) {
     return await Bot.unwrap<Chat>(this.request('/getPrivateChat', {
-      user_id: String(user),
+      user_id: user,
     }));
   }