Update kotlinVersion to v2.0.21

Author: renovate[bot]

build.gradle.kts

@@ -1,5 +1,5 @@
 plugins {
-  val kotlinVersion = "2.0.20"
+  val kotlinVersion = "2.0.21"
   kotlin("jvm") version kotlinVersion
   id("org.jetbrains.kotlin.plugin.compose") version kotlinVersion
   id("org.jetbrains.compose") version "1.6.11"