block candidate may communicate sigops as sigchecks post fork in coinbase tx

### Describe the issue
https://github.com/Bitcoin-ABC/bitcoin-abc/blob/master/src/miner.cpp#L237

After the may2020 fork coinbase tx should report 0 sigchecks, rather than the # of sigops in their output scripts.

I think that this field is output in getblocktemplate as "sigops". However, since I work on a different client, what you do with the field may have changed, potentially making this not-a-bug. If that is the case, sorry for wasting your time.

Start at src/miner.cpp#L237 and trace how the coinbase transaction’s sigops value is exposed through getblocktemplate. Check the May 2020 fork behavior and field meaning; done means the coinbase transaction reports 0 sigchecks rather than the number of sigops in its output scripts.

Written by the indexing model from the issue text.