Bump org.jetbrains.kotlin:kotlin-bom in /generators/kotlin/resources

Bumps [org.jetbrains.kotlin:kotlin-bom](https://github.com/JetBrains/kotlin) from 1.9.25 to 2.0.21.
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v2.0.21/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.9.25...v2.0.21)

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

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

generators/kotlin/resources/gradle/libs.versions.toml

@@ -1,4 +1,4 @@
 [libraries]
-kotlin = { module = 'org.jetbrains.kotlin:kotlin-bom', version = '1.9.25' }
+kotlin = { module = 'org.jetbrains.kotlin:kotlin-bom', version = '2.0.21' }
 
 mockito-kotlin = { module = 'org.mockito.kotlin:mockito-kotlin', version = '5.4.0' }