Bump kotlinVersion from 1.8.20 to 1.8.21

Bumps `kotlinVersion` from 1.8.20 to 1.8.21.

Updates `jvm` from 1.8.20 to 1.8.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.8.20...v1.8.21)

Updates `plugin.spring` from 1.8.20 to 1.8.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.8.20...v1.8.21)

Updates `plugin.jpa` from 1.8.20 to 1.8.21
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/master/ChangeLog.md)
- [Commits](JetBrains/kotlin@v1.8.20...v1.8.21)

---
updated-dependencies:
- dependency-name: jvm
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: plugin.spring
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: plugin.jpa
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

build.gradle.kts

@@ -5,7 +5,7 @@ val logstashVersion = "7.3"
 val testContainersVersion = "1.18.0"
 val springDocVersion = "2.1.0"
 val tokenValidationVersion = "3.0.11"
-val kotlinVersion = "1.8.20"
+val kotlinVersion = "1.8.21"
 
 repositories {
     mavenCentral()