Update the 'test_IsStandard' unit test
Update the 'test_IsStandard' unit test

The maximum length for the payload of an OP_RETURN output is now
80 bytes, and unit tests must be modified to account for the change.

syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin,syscoin/syscoin