Bump jvm from 1.9.20 to 1.9.21

Bumps [jvm](https://github.com/JetBrains/kotlin) from 1.9.20 to 1.9.21.
- [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: jvm
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

build.gradle.kts

@@ -2,7 +2,7 @@ import org.gradle.api.tasks.testing.logging.TestExceptionFormat
 
 plugins {
     id("java")
-    kotlin("jvm") version "1.9.20"
+    kotlin("jvm") version "1.9.21"
     id("com.github.johnrengelman.shadow") version "8.1.1"
     id("xyz.jpenilla.run-paper") version "2.2.2"
     id("net.minecrell.plugin-yml.bukkit") version "0.6.0"