build(deps): bump kotlin from 1.9.23 to 2.1.20

Bumps `kotlin` from 1.9.23 to 2.1.20.

Updates `org.jetbrains.kotlin:kotlin-test` 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)

Updates `org.jetbrains.kotlin.plugin.atomicfu` 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)

Updates `org.jetbrains.kotlin.multiplatform` 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)

Updates `org.jetbrains.kotlin.plugin.serialization` 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: org.jetbrains.kotlin:kotlin-test
  dependency-version: 2.1.20
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.jetbrains.kotlin.plugin.atomicfu
  dependency-version: 2.1.20
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.jetbrains.kotlin.multiplatform
  dependency-version: 2.1.20
  dependency-type: direct:production
  update-type: version-update:semver-major
- dependency-name: org.jetbrains.kotlin.plugin.serialization
  dependency-version: 2.1.20
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 agp = "8.1.1"
 compose = "1.7.1"
-kotlin = "1.9.23"
+kotlin = "2.1.20"
 coroutines = "1.8.0"
 voyager = "1.0.0-rc10"