modernized kotlin version

Author: holgerbrandl

build.gradle.kts

@@ -2,10 +2,10 @@ import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 import org.gradle.api.tasks.testing.logging.TestExceptionFormat
 import org.gradle.api.tasks.testing.logging.TestLogEvent
 
-val kotlinVersion: String = "1.6.10"
+val kotlinVersion: String = "1.6.20"
 
 plugins {
-    kotlin("jvm") version "1.6.10"
+    kotlin("jvm") version "1.6.20"
     id("com.github.johnrengelman.shadow") version "6.1.0"
 }