update rustls

## Problem

`cargo deny check` is complaining about our rustls versions, causing
CI to fail:

```
error[vulnerability]: `rustls::ConnectionCommon::complete_io` could fall into an infinite loop based on network input
    ┌─ /__w/neon/neon/Cargo.lock:395:1
    │
395 │ rustls 0.21.9 registry+https://github.com/rust-lang/crates.io-index
    │ ------------------------------------------------------------------- security vulnerability detected
    │
    = ID: RUSTSEC-2024-0336
    = Advisory: https://rustsec.org/advisories/RUSTSEC-2024-0336
    = If a `close_notify` alert is received during a handshake, `complete_io`
      does not terminate.

      Callers which do not call `complete_io` are not affected.

      `rustls-tokio` and `rustls-ffi` do not call `complete_io`
      and are not affected.

      `rustls::Stream` and `rustls::StreamOwned` types use
      `complete_io` and are affected.
    = Announcement: GHSA-6g7w-8wpp-frhj
    = Solution: Upgrade to >=0.23.5 OR >=0.22.4, <0.23.0 OR >=0.21.11, <0.22.0 (try `cargo update -p rustls`)

error[vulnerability]: `rustls::ConnectionCommon::complete_io` could fall into an infinite loop based on network input
    ┌─ /__w/neon/neon/Cargo.lock:396:1
    │
396 │ rustls 0.22.2 registry+https://github.com/rust-lang/crates.io-index
    │ ------------------------------------------------------------------- security vulnerability detected
    │
    = ID: RUSTSEC-2024-0336
    = Advisory: https://rustsec.org/advisories/RUSTSEC-2024-0336
    = If a `close_notify` alert is received during a handshake, `complete_io`
      does not terminate.

      Callers which do not call `complete_io` are not affected.

      `rustls-tokio` and `rustls-ffi` do not call `complete_io`
      and are not affected.

      `rustls::Stream` and `rustls::StreamOwned` types use
      `complete_io` and are affected.
    = Announcement: GHSA-6g7w-8wpp-frhj
    = Solution: Upgrade to >=0.23.5 OR >=0.22.4, <0.23.0 OR >=0.21.11, <0.22.0 (try `cargo update -p rustls`)
```

## Summary of changes

`cargo update -p rustls@0.21.9 -p rustls@0.22.2`