Update bindgen requirement from 0.70 to 0.71 (#98)

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/main/CHANGELOG.md)
- [Commits](rust-lang/rust-bindgen@v0.70.0...v0.71.0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

mupdf-sys/Cargo.toml

@@ -87,7 +87,7 @@ epub = []
 tesseract = []
 
 [build-dependencies]
-bindgen = { version = "0.70", default-features = false, features = ["runtime"] }
+bindgen = { version = "0.71", default-features = false, features = ["runtime"] }
 cc = "1.0.50"
 pkg-config = "0.3"