`round_num` and `block` no longer allowed when querying balances

### Subject of the issue

### Your environment

`py-algorand-sdk 2.0.0`

### Steps to reproduce

1. Call the method `asset_balances(asset_id, round_num=number)` or `asset_balances(asset_id, block=number)`

### Expected behaviour

A balance return at the given block/round number according to the docs: https://py-algorand-sdk.readthedocs.io/en/latest/algosdk/v2client/indexer.html

### Actual behaviour

It seems like the method got changed, and doesn't allow for this parameter anymore, I believe it's a case of outdated docs or an undocumented change, since I get the following TypeErrors:

`TypeError: IndexerClient.indexer_request() got an unexpected keyword argument 'round_num'`
`TypeError: IndexerClient.indexer_request() got an unexpected keyword argument 'block'`