Well, not really, the contrapositive is that if the series diverges the Riemann Hypothesis would be refuted. But few doubt that the Riemann Hypothesis is true. So using it as an assumption merely makes the convergence slightly iffy. For another example of its use, see the deterministic Miller primality test: https://en.wikipedia.org/wiki/Miller–Rabin_primality_test
Well, not really, the contrapositive is that if the series diverges the Riemann Hypothesis would be refuted. But few doubt that the Riemann Hypothesis is true. So using it as an assumption merely makes the convergence slightly iffy. For another example of its use, see the deterministic Miller primality test: https://en.wikipedia.org/wiki/Miller–Rabin_primality_test