build(deps): update jni requirement from 0.20 to 0.21

Updates the requirements on [jni](https://github.com/jni-rs/jni-rs) to permit the latest version.
- [Release notes](https://github.com/jni-rs/jni-rs/releases)
- [Changelog](https://github.com/jni-rs/jni-rs/blob/master/CHANGELOG.md)
- [Commits](jni-rs/jni-rs@v0.20.0...v0.21.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

ndk-examples/Cargo.toml

@@ -6,7 +6,7 @@ edition = "2018"
 publish = false
 
 [target.'cfg(target_os = "android")'.dependencies]
-jni = "0.20"
+jni = "0.21"
 libc = "0.2"
 log = "0.4.14"
 ndk = { version = "0.7", features = ["api-level-23"] }