Remove footgun doc comment in miner TX validation

This comment suggests this check is unnecessary, when it is completely necessary as miner TXs can have multiple outputs *which is a statement directly, and incorrectly, contradicted by this comment*. While I don't ever see someone removing this code and getting their edits merged into Monero, someone inexperienced who thinks they're cleaning old code may break their own work, and then there's really just zero benefit to keeping this around.

src/cryptonote_core/blockchain.cpp

@@ -1363,9 +1363,6 @@ bool Blockchain::prevalidate_miner_transaction(const block& b, uint64_t height,
   CHECK_AND_ASSERT_MES(b.miner_tx.unlock_time == height + CRYPTONOTE_MINED_MONEY_UNLOCK_WINDOW, false, "coinbase transaction transaction has the wrong unlock time=" << b.miner_tx.unlock_time << ", expected " << height + CRYPTONOTE_MINED_MONEY_UNLOCK_WINDOW);
 
   //check outs overflow
-  //NOTE: not entirely sure this is necessary, given that this function is
-  //      designed simply to make sure the total amount for a transaction
-  //      does not overflow a uint64_t, and this transaction *is* a uint64_t...
   if(!check_outs_overflow(b.miner_tx))
   {
     MERROR("miner transaction has money overflow in block " << get_block_hash(b));