Remove redundant block argument from Indexer client.

## Problem

The indexer client accepts redundant and error-causing parameters in a few of its methods. In particular:
* in several places the synonomous `block` and `round_num` are accepted. [EG here](https://github.com/algorand/py-algorand-sdk/blob/develop/algosdk/v2client/indexer.py#L189_L193)
* in several places we alert users with `DO NOT USE` a particular param. [EG here](https://github.com/algorand/py-algorand-sdk/blob/develop/algosdk/v2client/indexer.py#L836)

## Solution

Remove the offending parameters. As this is a breaking change, we may want to include it into a **V3** upgrade.
We can start by deprecating usage ASAP.

## Related Issues

#471

## Urgency

Medium - this is mostly a nuisance, but it does cause confusion