Bump kotlinVersion from 1.9.10 to 1.9.20 (#23)

Bumps `kotlinVersion` from 1.9.10 to 1.9.20.

Updates `org.jetbrains.kotlin.plugin.allopen` from 1.9.10 to 1.9.20
- [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)

Updates `jvm` from 1.9.10 to 1.9.20
- [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)

Updates `plugin.spring` from 1.9.10 to 1.9.20
- [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: org.jetbrains.kotlin.plugin.allopen
  dependency-type: direct:production
  update-type: version-update:semver-patch
- 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
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

build.gradle.kts

@@ -3,7 +3,7 @@ plugins {
     id("io.spring.dependency-management") version "1.1.3"
     id("org.jmailen.kotlinter") version "4.0.0"
     id("io.gitlab.arturbosch.detekt") version "1.23.1"
-    val kotlinVersion = "1.9.10"
+    val kotlinVersion = "1.9.20"
     id("org.jetbrains.kotlin.plugin.allopen") version kotlinVersion
     kotlin("jvm") version kotlinVersion
     kotlin("plugin.spring") version kotlinVersion