Bump kotlin from 2.0.10 to 2.0.21

Bumps `kotlin` from 2.0.10 to 2.0.21.

Updates `org.jetbrains.kotlin.multiplatform` from 2.0.10 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@v2.0.10...v2.0.21)

Updates `org.jetbrains.kotlin.plugin.serialization` from 2.0.10 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@v2.0.10...v2.0.21)

Updates `org.jetbrains.kotlin.plugin.allopen` from 2.0.10 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@v2.0.10...v2.0.21)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -1,5 +1,5 @@
 [versions]
-kotlin = "2.0.10"
+kotlin = "2.0.21"
 kotest = "5.9.1"
 detekt = "1.23.7"
 ktlint = "1.1.0"