Unnamed arguments are confusing as to what they mean without looking up
the function signature.
Since segwit is active by default in regtest, and all blocks are
serialized with witness (#15664, c459c5f), remove the argument
`with_witness=True` from all calls to `CBlock::serialize` and
`BlockTransactions::serialize`.
This diff has been created with a script, but is better reviewed without
a scripted diff.
sed -i --regexp-extended -e 's/block(_?[2a-z]*)\.serialize\([a-z_]*=?True/block\1.serialize(/g' $(git grep -l serialize ./test)