build(deps): bump org.jetbrains.kotlin.android in /13_auth/android

Bumps [org.jetbrains.kotlin.android](https://github.com/JetBrains/kotlin) from 2.0.10 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@v2.0.10...v2.0.21)

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

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

13_auth/android/build.gradle

@@ -1,6 +1,6 @@
 // Top-level build file where you can add configuration options common to all sub-projects/modules.
 buildscript {
-    ext.kotlin_version = "2.0.10"
+    ext.kotlin_version = "2.0.21"
     ext.android_gradle_version = "8.5.2"
 }