The TransactionRequest deserialization overflow test was ported in D5049 and adapted to fit our codebase and check the actual exception message. This include a test for an actually unreachable test case, which is added as a safety net in case the MAX_SIZE constant is bumped.
However after a refactor backported in D8790, this exception message is no longer the same as the overflow is now managed by the DifferenceFormatter. This diff fixes the error message.