Data is fetched twice in CSI500 index collector

[Chlorie]

https://github.com/microsoft/qlib/blob/98f569eed2252cc7fad0c120cad44f6181c3acf6/scripts/data_collector/cn_index/collector.py#L401-L408

result is overwritten with the call to self.get_data_from_baostock(date), and that function contains exactly the same code as the lines above the overwrite. Might be an oversight during refactoring.

[SunsetWolf]

Would you like to create a pull request to fix this issue.