chore(deps): bump kotlin.version from 2.4.20 to 2.4.21 (#3653)

Bumps `kotlin.version` from 2.4.20 to 2.4.21.

Updates `org.jetbrains.kotlin:kotlin-stdlib` from 2.4.20 to 2.4.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.4.20...v2.4.21)

Updates `org.jetbrains.kotlin:kotlin-maven-plugin` from 2.4.20 to 2.4.21

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-stdlib
  dependency-version: 2.4.21
  dependency-type: direct:development
  update-type: version-update:semver-patch
- dependency-name: org.jetbrains.kotlin:kotlin-maven-plugin
  dependency-version: 2.4.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

sample-operators/kotlin-operator/pom.xml

@@ -33,7 +33,7 @@
     Kotlin</description>
 
   <properties>
-    <kotlin.version>2.4.20</kotlin.version>
+    <kotlin.version>2.4.21</kotlin.version>
   </properties>
 
   <dependencyManagement>