[doc] Remove outdated comment about mining code ignoring CPFP
[doc] Remove outdated comment about mining code ignoring CPFP

BlockAssembler chooses transactions on the basis of packages (which incorporate
unconfirmed ancestors into feerate), so the specified RBF comment about mining
code ignoring CPFP is out of date.

chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin,chaincoin/chaincoin