chore(deps): bump kotlin.version from 1.8.10 to 1.9.21

Bumps `kotlin.version` from 1.8.10 to 1.9.21.

Updates `org.jetbrains.kotlin:kotlin-bom` from 1.8.10 to 1.9.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.8.10...v1.9.21)

Updates `org.jetbrains.kotlin:kotlin-maven-plugin` from 1.8.10 to 1.9.21

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-bom
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.jetbrains.kotlin:kotlin-maven-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

pom.xml

@@ -65,7 +65,7 @@
 
 		<netty.version>4.1.101.Final</netty.version>
 
-		<kotlin.version>1.8.10</kotlin.version>
+		<kotlin.version>1.9.21</kotlin.version>
 		<!-- https://kotlinlang.org/docs/maven.html#specifying-compiler-options -->
 		<kotlin.compiler.apiVersion>1.5</kotlin.compiler.apiVersion>
 		<kotlin.compiler.jvmTarget>${maven.compiler.source}</kotlin.compiler.jvmTarget>