delete unused test support function which prompts a compiler warning

[mars-risc0]

this was fixed in risczero-wip, but either didn't land or otherwise didn't make it to the zirgen repo

[shkoo]

@tzerrell, best I can tell we get test coverage with the makeConstOneTest, so we don't need the makeConstZeroTest so this looks good to me, but please chime in if it isn't!

[tzerrell]

Yes, this is good, this was meant to be a simpler variant that might pass when the makeConstOneTest would fail, but because the input was unnecessary it actually created more problems without testing anything relevant beyond what makeConstOneTest tests