Precondition panic on Rust 1.78 due to outdated stun_codec

[jfro]

Looks like stun_codec has had the issue resolved in the 0.3 releases, but running in debug profile stunclient against stun_codec 0.2 will yield a precondition panic:

thread 'main' panicked at library/core/src/panicking.rs:156:5:
unsafe precondition(s) violated: slice::get_unchecked_mut requires that the index is within the slice```

hopefully updating the dep is fairly painless, haven't tried yet but will PR if I find a moment to.