RUST-2447 Update RustCrypto dependencies to remove block-buffer 0.10.4

[devleadm]

Hi MongoDB Rust driver team,

`mongodb 3.7.0` still pulls `block-buffer 0.10.4` through older RustCrypto dependencies.

Security scanner finding:

- Package: `block-buffer 0.10.4`
- Advisory: `sonatype-2026-003895`
- Severity: 8.2

Dependency path from `mongodb 3.7.0`:

```text
mongodb 3.7.0
  -> hmac 0.12.1 / md-5 0.10.6 / pbkdf2 0.12.2 / sha1 0.10.6 / sha2 0.10.9
  -> digest 0.10.7
  -> block-buffer 0.10.4

I checked the current main branch. In driver/Cargo.toml, these dependencies still use old RustCrypto versions:

hmac = "0.12.1"
md-5 = "0.10.1"
sha1 = "0.10.0"
sha2 = "0.10.2"

I also saw this merged dependency PR:

#1722

But main still contains block-buffer 0.10.4 and digest 0.10.7 in Cargo.lock.

Can MongoDB Rust driver update these RustCrypto dependencies, so that mongodb no longer pulls digest 0.10.7 and block-buffer 0.10.4?

Thank you.

[abr-egn]

Thanks for bringing this to our attention! bd447a6 fixes this and will go out as part of the 3.8.0 release later this week.