Fix rust-bindgen ident issue

[NgaiJustin]

Currently the btor2tools does not build. It panics with the following error

thread 'main' panicked at '"Btor2Sort_union_(anonymous_at_/.../target/debug/build/btor2tools-sys-54a31d899707ee43/out/btor2tools-src/src/btor2parser/btor2parser_h_139_3)" is not a valid Ident', .../.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro2-1.0.69/src/fallback.rs:817:9

The issue is outlined here. It is resolved in later versions, specifically >=0.62.0

• thread 'main' panicked at '"__mbstate_t_(anonymous_struct_at_foo_cc_2_3)" is not a valid Ident' rust-lang/rust-bindgen#2312

There are many other instances (such as this) of fixes with just bumping the build dependency

[ChristianMoesl]

Thanks for the PR! I wasn't able to reproduce that error, when running the CI pipeline: https://github.com/ChristianMoesl/btor2tools-sys/actions/runs/6812725407
So I guess, this problem occurs with a specific version of LLVM!?

Anyway, I think it's a good call to bump the bindgen version anyway, so I'll merge it.