build(deps): bump jni from 0.19.0 to 0.21.1

Bumps [jni](https://github.com/jni-rs/jni-rs) from 0.19.0 to 0.21.1.
- [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@v0.19.0...v0.21.1)

---
updated-dependencies:
- dependency-name: jni
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

boringtun/Cargo.toml

@@ -40,7 +40,7 @@ chacha20poly1305 = "0.10.0-pre.1"
 aead = "0.5.0-pre.2"
 blake2 = "0.10"
 hmac = "0.12"
-jni = { version = "0.19.0", optional = true }
+jni = { version = "0.21.1", optional = true }
 mock_instant = { version = "0.3", optional = true }
 socket2 = { version = "0.4.7", features = ["all"], optional = true }
 thiserror = { version = "1", optional = true }