Bump kotlin from 2.3.20 to 2.3.21

Bumps `kotlin` from 2.3.20 to 2.3.21.

Updates `org.jetbrains.kotlin.plugin.compose` from 2.3.20 to 2.3.21
- [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 `org.jetbrains.kotlin.plugin.serialization` from 2.3.20 to 2.3.21
- [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.compose
  dependency-version: 2.3.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
- dependency-name: org.jetbrains.kotlin.plugin.serialization
  dependency-version: 2.3.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

gradle/libs.versions.toml

@@ -1,6 +1,6 @@
 [versions]
 agp = "9.1.0"
-kotlin = "2.3.20"
+kotlin = "2.3.21"
 core-ktx = "1.18.0"
 junit = "4.13.2"
 androidx-test-ext-junit = "1.3.0"