[58_maintenance] chore: update webpki dependencies to fix cargo audit CI (#11794)

# Which issue does this PR close?

- Part of #11665 (58.4.1 release)

# Rationale for this change

The `Audit` job fails on `58_maintenance` because two advisories were
published against versions pinned in the committed `Cargo.lock`:

- RUSTSEC-2026-0382: `rustls-webpki` 0.103.15 (fixed in 0.103.16)
- RUSTSEC-2026-0381: `webpki-roots` 1.0.9 (fixed in 1.0.10)

Reproduced locally by running the CI `cargo audit` invocation (with the
workflow's `--ignore` list) against the branch, which reports exactly
these two vulnerabilities.

This is the same fix as #11752 on `main` and #11793 on `59_maintenance`.

# What changes are included in this PR?

Update only the two flagged crates in `Cargo.lock`:

```
cargo update -p rustls-webpki -p webpki-roots
```

Verified locally that the CI `cargo audit` invocation passes afterwards,
and that the lockfile resolves with `cargo +1.85.0 metadata --locked`.
Both new versions have `rust-version = "1.71"`, below the workspace MSRV
of 1.85.

# Are these changes tested?

CI

# Are there any user-facing changes?

No. This only affects the lockfile used for workspace builds and CI.

Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

Author: alamb