Bump plugin.serialization from 2.2.10 to 2.2.21

Bumps [plugin.serialization](https://github.com/JetBrains/kotlin) from 2.2.10 to 2.2.21.
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.2.10...v2.2.21)

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

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

Author: dependabot[bot]

build.gradle.kts

@@ -2,7 +2,7 @@ plugins {
     kotlin("jvm") version "2.2.21"
     id("org.jlleitschuh.gradle.ktlint") version "11.5.0"
     application
-    kotlin("plugin.serialization") version "2.2.10"
+    kotlin("plugin.serialization") version "2.2.21"
 }
 
 group = "io.github.mojira"