Update bindgen requirement from 0.52 to 0.53 in /fitsio-sys-bindgen
Update bindgen requirement from 0.52 to 0.53 in /fitsio-sys-bindgen

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/v0.52.0...v0.53.0)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
mindriot101/rust-fitsio,mindriot101/rust-fitsio,mindriot101/rust-fitsio,mindriot101/rust-fitsio,mindriot101/rust-cfitsio,mindriot101/rust-fitsio,mindriot101/rust-cfitsio