fix(fuzz): remove invalid assertion in decode_tx harness

The decode_tx fuzz target asserted that DecodeHexTx() always fails,
inherited from Bitcoin Core where random fuzz bytes essentially never
produce valid transactions. With real Dash chain data as corpus input
(e.g. AssetUnlockTx), valid transactions decode successfully, causing
a false-positive crash. Remove the assertion to allow both success
and failure paths to be exercised.

Author: thepastaclaw

src/test/fuzz/decode_tx.cpp

@@ -16,6 +16,5 @@ FUZZ_TARGET(decode_tx)
 {
     const std::string tx_hex = HexStr(std::string{buffer.begin(), buffer.end()});
     CMutableTransaction mtx;
-    const bool result_none = DecodeHexTx(mtx, tx_hex);
-    assert(!result_none);
+    (void)DecodeHexTx(mtx, tx_hex);
 }