Gradle: Bump jvm from 1.9.23 to 2.1.20

Bumps [jvm](https://github.com/JetBrains/kotlin) from 1.9.23 to 2.1.20.
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.9.23...v2.1.20)

---
updated-dependencies:
- dependency-name: jvm
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

build.gradle.kts

@@ -6,7 +6,7 @@ import kotlinx.kover.gradle.plugin.dsl.KoverProjectExtension
 import org.gradle.kotlin.dsl.implementation
 
 plugins {
-  val kotlinVersion = "2.0.21"
+  val kotlinVersion = "2.1.20"
   kotlin("jvm") version kotlinVersion
   id("com.diffplug.spotless") version "7.0.3"
   id("org.springframework.boot") version "3.4.4" apply false