去掉setChannelsAttribute，框架可自动转换

app/Models/UserChannel.php

@@ -12,13 +12,9 @@ class UserChannel extends BaseModel
 {
     use HasFactory;
 
+    // 获取时需要转换，写入时框架可自动将数组转换后保存
     public function getChannelsAttribute($value)
     {
         return json_decode($value, true);
     }
-
-    public function setChannelsAttribute($value)
-    {
-        return json_encode($value);
-    }
 }