Bump kotlin.version from 2.0.20 to 2.0.21

Bumps `kotlin.version` from 2.0.20 to 2.0.21.

Updates `org.jetbrains.kotlin:kotlin-stdlib` from 2.0.20 to 2.0.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v2.0.21/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.0.20...v2.0.21)

Updates `org.jetbrains.kotlin:kotlin-maven-plugin` from 2.0.20 to 2.0.21

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

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

Author: dependabot[bot]

pom.xml

@@ -13,7 +13,7 @@
         <maven.compiler.source>${java.version}</maven.compiler.source>
         <maven.compiler.target>${java.version}</maven.compiler.target>
         <maven-compiler.release>${java.version}</maven-compiler.release>
-        <kotlin.version>2.0.20</kotlin.version>
+        <kotlin.version>2.0.21</kotlin.version>
 
         <maven-compiler-plugin.version>3.13.0</maven-compiler-plugin.version>
         <maven-dependency-plugin.version>3.8.0</maven-dependency-plugin.version>