Revert "Bump org.jetbrains.kotlin.jvm from 1.6.21 to 1.8.20"

This reverts commit 19a0470.

Author: harikrishnan83

build.gradle

@@ -6,7 +6,7 @@
 
 plugins {
     // Apply the Kotlin JVM plugin to add support for Kotlin.
-    id 'org.jetbrains.kotlin.jvm' version '1.8.20'
+    id 'org.jetbrains.kotlin.jvm' version '1.6.21'
 
     // Apply the application plugin to add support for building a CLI application.
     id 'application'