build(deps): update bindgen requirement from 0.59 to 0.60

Updates the requirements on [bindgen](https://github.com/rust-lang/rust-bindgen) to permit the latest version.
- [Release notes](https://github.com/rust-lang/rust-bindgen/releases)
- [Changelog](https://github.com/rust-lang/rust-bindgen/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-lang/rust-bindgen/compare/v0.59.0...v0.60.1)

---
updated-dependencies:
- dependency-name: bindgen
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

aya-gen/Cargo.toml

@@ -5,7 +5,7 @@ authors = ["Alessandro Decina <alessandro.d@gmail.com>"]
 edition = "2018"
 
 [dependencies]
-bindgen = "0.59"
+bindgen = "0.60"
 structopt = {version = "0.3", default-features = false }
 anyhow = "1"
 thiserror = "1"