Remove hardcoded shard number from prototype

[gabehamilton]

In the initial prototype where S3 fetch time was a major impediment, number of shards was hardcoded to 4 in the runner.
https://github.com/near/queryapi/blob/main/runner/src/lake-client/lake-client.ts#L80

Now that we have some pre-fetching strategies let's return to pulling that from the block.json or move it to config.

[pkudinov]

Duplicated by #423

[gabehamilton]

Confirmed that the affected code was fixed in #423

[morgsmccauley]

This is still an issue:

• queryapi/runner/src/lake-client/lake-client.ts

  Line 80 in 7655aef

  const shardsPromises = await this.fetchShardsPromises(blockHeight, 4);

• queryapi/block-server/handler.js

  Line 40 in 7655aef

  const shardsPromises = await fetchShardsPromises(block_height, 4, options); // block.chunks.length)