Update plugin org.jetbrains.kotlin.jvm to v2.1.21 (#83)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| org.jetbrains.kotlin.jvm | `2.1.20` -> `2.1.21` |
[![age](https://developer.mend.io/api/mc/badges/age/maven/org.jetbrains.kotlin.jvm:org.jetbrains.kotlin.jvm.gradle.plugin/2.1.21?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/maven/org.jetbrains.kotlin.jvm:org.jetbrains.kotlin.jvm.gradle.plugin/2.1.21?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/maven/org.jetbrains.kotlin.jvm:org.jetbrains.kotlin.jvm.gradle.plugin/2.1.20/2.1.21?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/maven/org.jetbrains.kotlin.jvm:org.jetbrains.kotlin.jvm.gradle.plugin/2.1.20/2.1.21?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

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build.gradle.kts

@@ -41,7 +41,7 @@ object PluginProperties {
 
 plugins {
     `java-gradle-plugin`
-    kotlin("jvm") version "2.1.20"
+    kotlin("jvm") version "2.1.21"
     id("maven-publish")
     id("com.gradle.plugin-publish") version "1.3.1"
     id("org.jlleitschuh.gradle.ktlint") version "12.2.0"