Cargo update before v8.1.0

[michaelsproul]

Description

We should do a cargo update, or at least a cargo update -p tokio to silence the warning about the bug in tokio (https://github.com/sigp/lighthouse/security/dependabot/68). We're not actually vulnerable to this bug (we do not misuse tokio in a way that would trigger the issue), but it would still be nice to update.

Additional Info

We could chill on this issue until a few other refactor PRs which touch the Cargo.lock are merged:

• Prepare sensitive_url for crates.io #8223
• Remove context_deserialize and import from crates.io #8172
• Remove ethers-core from execution_layer #8149
• Migrate execution_engine_integration to alloy #8140
• Migrate the deposit_contract crate to alloy #8139