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-bom` 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-allopen` from 2.0.20 to 2.0.21

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

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

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-bom
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.jetbrains.kotlin:kotlin-maven-allopen
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.jetbrains.kotlin:kotlin-maven-noarg
  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] <[email protected]>

pom.xml

@@ -21,7 +21,7 @@
     <jgiven-kotlin.version>1.3.1.0</jgiven-kotlin.version>
 
     <java.version>17</java.version>
-    <kotlin.version>2.0.20</kotlin.version>
+    <kotlin.version>2.0.21</kotlin.version>
     <kotlin.compiler.incremental>true</kotlin.compiler.incremental>
     <kotlin.compiler.jvmTarget>${java.version}</kotlin.compiler.jvmTarget>
     <maven.compiler.source>${java.version}</maven.compiler.source>