Merge bitcoin/bitcoin#29516: test: removes unnecessary check from validation_tests

6ee3997 test: removes unnecessary check from validation_tests (Sergi Delgado Segura)

Pull request description:

  An unnecessary check was added to the block mutation tests in #29412 where IsBlockMutated is returning true for the invalid reasons: we try to check mutation via transaction duplication, but the merkle root is not updated before the check, therefore the check fails because the provided root and the computed root differ, but not because the block contains the same transaction twice.

  Notice that a proper check to test the duplication case is added a few lines later, so this check is just meaningless and can be removed. Check bitcoin/bitcoin#29412 (comment) for context.

ACKs for top commit:
  maflcko:
    ACK 6ee3997
  dergoegge:
    utACK 6ee3997
  BrandonOdiwuor:
    utACK 6ee3997

Tree-SHA512: e4627668091dda5f589e4c15edac39dc84aabc9b34b8f7fadbf512beb7111d5477e1b69567a34b4a657e48ba66dfb864db5ff37c9bbe3ff24cd32931b2dd89e6

Author: fanquake

src/test/validation_tests.cpp

@@ -233,7 +233,6 @@ BOOST_AUTO_TEST_CASE(block_malleation)
         // Block with two transactions is mutated if any node is duplicate.
         {
             block.vtx[1] = block.vtx[0];
-            BOOST_CHECK(is_mutated(block, /*check_witness_root=*/false));
             HashWriter hasher;
             hasher.write(block.vtx[0]->GetHash());
             hasher.write(block.vtx[1]->GetHash());