chore(deps): bump kotlin from 2.2.20 to 2.2.21

Bumps `kotlin` from 2.2.20 to 2.2.21.

Updates `org.jetbrains.kotlin.jvm` from 2.2.20 to 2.2.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v2.2.21/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.2.20...v2.2.21)

Updates `org.jetbrains.kotlin.plugin.serialization` from 2.2.20 to 2.2.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v2.2.21/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.2.20...v2.2.21)

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin.jvm
  dependency-version: 2.2.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.jetbrains.kotlin.plugin.serialization
  dependency-version: 2.2.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -4,7 +4,7 @@ jetty9 = "9.4.57.v20241219"
 jgit = "7.4.0.202509020913-r"
 junit = "5.13.4"
 keycloak="26.4.0"
-kotlin = "2.2.20"
+kotlin = "2.2.21"
 kotlin-logging = "3.0.5"
 kotlinSerialization="1.9.0"
 kotlinx-coroutines = "1.10.2"