Bump `cargo-deny-action` and fix clippy suggestions

[brycx]

A few maintenance changes:

• Update cargo-deny-action to 2.0.1
• Include 2024 in SHA3 copyright header
• Satisfy new clippy lints
• Remove one test from SHA2 that checked for panic on overflow with 64-bit int, but this is useless because
  1. We don't run CI in 128-bit targets
  2. Rust has no longer any 128-bit targets listed in their supported target (I'm pretty sure there were some at one point, haven't found it though)
  3. The pointer target width doesn't even have 128 so we can't check it (thanks for catching this clippy)

@vlmutolo do you happen to have time to check this through? should mostly be trivial changes but there's a few of them