build(deps): Bump kotlin from 2.3.20 to 2.3.21

Bumps `kotlin` from 2.3.20 to 2.3.21.

Updates `org.jetbrains.kotlin:kotlin-test` from 2.3.20 to 2.3.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.3.20...v2.3.21)

Updates `org.jetbrains.kotlin.multiplatform` from 2.3.20 to 2.3.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.3.20...v2.3.21)

Updates `org.jetbrains.kotlin.plugin.serialization` from 2.3.20 to 2.3.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.3.20...v2.3.21)

Updates `org.jetbrains.kotlin.jvm` from 2.3.20 to 2.3.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.3.20...v2.3.21)

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-test
  dependency-version: 2.3.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.jetbrains.kotlin.multiplatform
  dependency-version: 2.3.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.jetbrains.kotlin.plugin.serialization
  dependency-version: 2.3.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.jetbrains.kotlin.jvm
  dependency-version: 2.3.21
  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

@@ -6,7 +6,7 @@ jsonSchemaValidator = "3.0.1"
 jsonSchemaValidatorVersion = "0.5.4"
 junit = "4.13.2"
 junitJupiter = "6.0.3"
-kotlin = "2.3.20"
+kotlin = "2.3.21"
 kotlinxCoroutines = "1.10.2"
 kotlinBrowser = "0.5.0"
 android-minSdk = "24"