Update csbindgen requirement from =1.9.0 to =1.9.3 (microsoft#292)

Updates the requirements on [csbindgen](https://github.com/Cysharp/csbindgen) to permit the latest version.
- [Release notes](https://github.com/Cysharp/csbindgen/releases)
- [Commits](Cysharp/csbindgen@1.9.0...1.9.3)

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

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

bindings/ffi/Cargo.toml

@@ -21,4 +21,4 @@ custom_allocator = []
 
 [build-dependencies]
 cbindgen = "0.26.0"
-csbindgen = "=1.9.0"
+csbindgen = "=1.9.3"