Bump kotlin_version from 1.5.31 to 1.6.0

Bumps `kotlin_version` from 1.5.31 to 1.6.0.

Updates `kotlin-gradle-plugin` from 1.5.31 to 1.6.0
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](https://github.com/JetBrains/kotlin/commits)

Updates `kotlin-stdlib` from 1.5.31 to 1.6.0
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](https://github.com/JetBrains/kotlin/commits)

---
updated-dependencies:
- dependency-name: org.jetbrains.kotlin:kotlin-gradle-plugin
  dependency-type: direct:production
  update-type: version-update:semver-minor
- dependency-name: org.jetbrains.kotlin:kotlin-stdlib
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

build.gradle

@@ -9,7 +9,7 @@ import org.gradle.internal.jvm.Jvm
 // its root folder, another one for the app module in subfolder of root.
 
 buildscript {
-    ext.kotlin_version = '1.5.31'
+    ext.kotlin_version = '1.6.0'
     ext.jacoco_version = '0.8.7'
     repositories {
         google()