Update org.jetbrains.kotlin to v2.0.21

Author: renovate[bot]

build.gradle.kts

@@ -14,8 +14,8 @@ plugins {
     id("com.diffplug.spotless") version "6.25.0"
     id("org.domaframework.doma.codegen") version "3.0.0"
     id("org.domaframework.doma.compile") version "3.0.1"
-    kotlin("jvm") version "2.0.20"
-    kotlin("kapt") version "2.0.20"
+    kotlin("jvm") version "2.0.21"
+    kotlin("kapt") version "2.0.21"
 }
 
 kotlin {