Update cbindgen requirement from 0.26.0 to 0.27.0 (#296)

Updates the requirements on [cbindgen](https://github.com/mozilla/cbindgen) to permit the latest version.
- [Release notes](https://github.com/mozilla/cbindgen/releases)
- [Changelog](https://github.com/mozilla/cbindgen/blob/master/CHANGES)
- [Commits](https://github.com/mozilla/cbindgen/compare/0.26.0...v0.27.0)

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

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

bindings/ffi/Cargo.toml

@@ -20,5 +20,5 @@ coverage = ["regorus/coverage"]
 custom_allocator = []
 
 [build-dependencies]
-cbindgen = "0.26.0"
+cbindgen = "0.27.0"
 csbindgen = "=1.9.3"