[doc] Remove outdated comment about mining code ignoring CPFP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code ignoring CPFP is out of date.

Author: jamesob

src/validation.cpp

@@ -806,13 +806,11 @@ static bool AcceptToMemoryPoolWorker(const CChainParams& chainparams, CTxMemPool
                 // be increased is also an easy-to-reason about way to prevent
                 // DoS attacks via replacements.
                 //
-                // The mining code doesn't (currently) take children into
-                // account (CPFP) so we only consider the feerates of
-                // transactions being directly replaced, not their indirect
-                // descendants. While that does mean high feerate children are
-                // ignored when deciding whether or not to replace, we do
-                // require the replacement to pay more overall fees too,
-                // mitigating most cases.
+                // We only consider the feerates of transactions being directly
+                // replaced, not their indirect descendants. While that does
+                // mean high feerate children are ignored when deciding whether
+                // or not to replace, we do require the replacement to pay more
+                // overall fees too, mitigating most cases.
                 CFeeRate oldFeeRate(mi->GetModifiedFee(), mi->GetTxSize());
                 if (newFeeRate <= oldFeeRate)
                 {