Bump failure_derive and synstruture dependencies

Your crate has several transitive dependencies that use an old version
of the `syn` crate. In future versions of Rust (in particular, once
rust-lang/rust#77153) is merged), this may cause
your crate to stop compiling.

Fortunately, all of these crates have newer versions available when
depend on newer versions of `syn`. I've updated these crates in your
`Cargo.lock`, which will allow your crate to compile on both older and
newer versions of Rust.