Hiya I agree with Jane, wetting a (clean )wound could potentially make it more likely for bacteria to develop in the moist skin.
Risk of infection should be low post neuter as the vet will (I hope) have followed strict hygiene practices for surgery.
I only use saline on bites or wounds that are at high risk of infection. I have only ever used saline on a spay wound once, on the rare occasion local infection begins.
I do give bunnies Baytril post op for neutering , as at least that prevents any nasty internal infection developing, and does seem to speed up healing of the wound site. Vets vary on their view on this though.