Merge #18379: doc: Comment fix merkle.cpp

5b59a19 Update merkle.cpp (4d55397500)

Pull request description:

  Change comment from `The reason is that if the number of hashes in the list at a given time
  is odd`, to ` The reason is that if the number of hashes in the list at a given level
         is odd` (to be a bit more precise: replacing `time` with `level`)

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ACKs for top commit:
  MarcoFalke:
    ACK 5b59a19
  instagibbs:
    ACK bitcoin/bitcoin@5b59a19

Tree-SHA512: 30d29b9855b30de8b54033ca4884cfb5bf8ab9e52cf61da237abba0e15ebff947c65f8ba82175694bc60ee0d54f940a098cadcb0404d3c3bcf577006ab0561a5

Author: MarcoFalke

src/consensus/merkle.cpp

@@ -10,7 +10,7 @@
        that the following merkle tree algorithm has a serious flaw related to
        duplicate txids, resulting in a vulnerability (CVE-2012-2459).
 
-       The reason is that if the number of hashes in the list at a given time
+       The reason is that if the number of hashes in the list at a given level
        is odd, the last one is duplicated before computing the next level (which
        is unusual in Merkle trees). This results in certain sequences of
        transactions leading to the same merkle root. For example, these two