chore(deps): bump org.jetbrains.kotlin.plugin.serialization (#434)

Bumps [org.jetbrains.kotlin.plugin.serialization](https://github.com/JetBrains/kotlin) 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.plugin.serialization
  dependency-version: 2.3.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -1,6 +1,6 @@
 [versions]
 #jetbrains
-kotlin = "2.3.20"
+kotlin = "2.3.21"
 kotlinxSerializationJson = "1.11.0"
 #KSP
 ksp = "2.3.7"