fix baidufanyi param error (#3053)

### What problem does this PR solve?

#3052

### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

agent/component/baidufanyi.py

         self.domain = 'finance'
 
     def check(self):
-        self.check_positive_integer(self.top_n, "Top N")
         self.check_empty(self.appid, "BaiduFanyi APPID")
         self.check_empty(self.secret_key, "BaiduFanyi Secret Key")
         self.check_valid_value(self.trans_type, "Translate type", ['translate', 'fieldtranslate'])