chore(deps): bump plugin.serialization from 2.3.20 to 2.3.21

Bumps plugin.serialization from 2.3.20 to 2.3.21.

---
updated-dependencies:
- dependency-name: plugin.serialization
  dependency-version: 2.3.21
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

build.gradle.kts

@@ -4,7 +4,7 @@ import java.net.URI
 plugins {
     application
     kotlin("jvm") version "2.3.20"
-    kotlin("plugin.serialization") version "2.3.20"
+    kotlin("plugin.serialization") version "2.3.21"
     jacoco
     id("org.sonarqube") version "6.2.0.5505"
 }