Bump org.jetbrains.kotlin.jvm from 1.6.20 to 1.9.21

Bumps [org.jetbrains.kotlin.jvm](https://github.com/JetBrains/kotlin) from 1.6.20 to 1.9.21.
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.6.20...v1.9.21)

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

Signed-off-by: dependabot[bot] <[email protected]>

build.gradle

@@ -1,5 +1,5 @@
 plugins {
-    id 'org.jetbrains.kotlin.jvm' version '1.6.20'
+    id 'org.jetbrains.kotlin.jvm' version '1.9.21'
     id 'com.github.johnrengelman.shadow' version '7.1.2'
 }