update anserini REST API integration

[sahel-sh]

With anserini rest API gone, we need to use the newly added Pyserini Rest API

[XiandaDu]

Hi I can help with this one

[sahel-sh]

@lilyjge would be your best point of contact on how to proceed with this one

[lilyjge]

Happy to help! Feel free to DM me on slack :)