cryptonote_basic: remove redundant call to get_transaction_hash() in overload

Issue noticed by DataHoarder.

src/cryptonote_basic/cryptonote_format_utils.cpp

@@ -1298,7 +1298,6 @@ namespace cryptonote
   crypto::hash get_transaction_hash(const transaction& t)
   {
     crypto::hash h = null_hash;
-    get_transaction_hash(t, h, NULL);
     CHECK_AND_ASSERT_THROW_MES(get_transaction_hash(t, h, NULL), "Failed to calculate transaction hash");
     return h;
   }