types: fix getblockstats txs field doc

[satsfy]

Docs are wrong in getblockstats txs field. The txs field counts all transactions in the block including the coinbase. Core's source passes block.vtx.size() directly, which includes the coinbase transaction at index 0. Bitcoin Core doc agrees.

Example, I just called

bitcoin-cli -regtest generatetoaddress 101 (bitcoin-cli -regtest getnewaddress)

Now I run

bitcoin-cli -regtest getblockstats 50 | grep "\"txs\""
  "txs": 1,

Returns 1 because that is the coinbase transaction.

[jamillambert]

I checked the docs and it looks like this changed in v20, i.e. v17-19 say (excluding coinbase). I didn't check if it actually changed or the docs were fixed. I say this because I know of other cases where the docs in v17 or so were incorrect.