Bump io.nats:jnats from 2.20.2 to 2.21.4 in /examples

Bumps [io.nats:jnats](https://github.com/nats-io/nats.java) from 2.20.2 to 2.21.4.
- [Release notes](https://github.com/nats-io/nats.java/releases)
- [Changelog](https://github.com/nats-io/nats.java/blob/main/CHANGELOG.md)
- [Commits](nats-io/nats.java@2.20.2...2.21.4)

---
updated-dependencies:
- dependency-name: io.nats:jnats
  dependency-version: 2.21.4
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

examples/nats/build.gradle

@@ -9,7 +9,7 @@ repositories {
 dependencies {
     testImplementation 'org.assertj:assertj-core:3.26.3'
     testImplementation 'org.testcontainers:testcontainers'
-    testImplementation 'io.nats:jnats:2.20.2'
+    testImplementation 'io.nats:jnats:2.21.4'
     testImplementation 'ch.qos.logback:logback-classic:1.3.14'
     testImplementation 'org.apache.httpcomponents:httpclient:4.5.14'
     testImplementation 'org.junit.jupiter:junit-jupiter:5.13.3'