Update plugin org.jetbrains.kotlin.jvm to v2.0.21

Author: renovate[bot]

build.gradle.kts

@@ -1,5 +1,5 @@
 plugins {
-    kotlin("jvm") version "2.0.20"
+    kotlin("jvm") version "2.0.21"
     id("com.github.johnrengelman.shadow") version "8.1.1"
     id("org.jlleitschuh.gradle.ktlint") version "12.1.1"
     `maven-publish`