Update rustls to address RUSTSEC-2026-0285 (#114)

This PR bumps the locked `rustls` from 0.23.29 to 0.23.45 (along with the `rustls-webpki` 0.103.15 it requires) to clear RUSTSEC-2026-0285, in which TLS 1.3 handshake messages were accepted across encryption level boundaries. The advisory was published on 14 September and has been failing the audit job on every run since. The crate only reaches the workspace through the Rust client's optional `fetch` feature via `solana-rpc-client` and `reqwest`, so this is a lockfile-only change with no manifest edits.

Author: lorisleiva