Wrong flag used for (set_)ipv6_multicast_hops

v1.1.4

https://github.com/bytecodealliance/rustix/blob/035acdc416d9465abc937bd8cd6a0031afc170aa/src/backend/linux_raw/net/sockopt.rs#L568-L571

https://github.com/bytecodealliance/rustix/blob/035acdc416d9465abc937bd8cd6a0031afc170aa/src/backend/libc/net/sockopt.rs#L617-L620

These two cases (and their getter counterparts) should use `IPPROTO_IPV6`, not `IPPROTO_IP`.

A library I use had to work around this bug:
https://github.com/al8n/hick/pull/49/changes#diff-5f92e53a99f51d3b30937d394280111bf28c84ff3f340c6ad82a08364d2e0cb0R24-R32

I'm just here making sure the issue got reported upstream. 🫡

Inizia leggendo le sezioni indicate in src/backend/linux_raw/net/sockopt.rs e src/backend/libc/net/sockopt.rs, quindi individua i getter corrispondenti per ipv6_multicast_hops. Verifica che i casi setter e getter interessati utilizzino IPPROTO_IPV6 anziché IPPROTO_IP e conferma che i test pertinenti delle opzioni socket abbiano esito positivo.

Scritto dal modello di indicizzazione a partire dal testo della issue.