message: refactor: CTxMemPool::IsUnbroadcastTx() requires CTxMemPool::cs lock
  No change in behavior, the lock is already held at call sites.
diff: @@ -736,9 +736,10 @@ public:
  }
  /** Returns whether a txid is in the unbroadcast set */
  - bool IsUnbroadcastTx(const uint256& txid) const {
  - LOCK(cs);
  - return (m_unbroadcast_txids.count(txid) != 0);
  + bool IsUnbroadcastTx(const uint256& txid) const EXCLUSIVE_LOCKS_REQUIRED(cs)
  + {
  + AssertLockHeld(cs);
  + return m_unbroadcast_txids.count(txid) != 0;
  }
  private:
  