Bump org.jetbrains.kotlin.android from 2.0.20 to 2.0.21 in /android

Bumps [org.jetbrains.kotlin.android](https://github.com/JetBrains/kotlin) from 2.0.20 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@v2.0.20...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] <support@github.com>

android/settings.gradle

@@ -20,7 +20,7 @@ pluginManagement {
 plugins {
     id "dev.flutter.flutter-plugin-loader" version "1.0.0"
     id "com.android.application" version '8.7.0' apply false
-    id "org.jetbrains.kotlin.android" version "2.0.20" apply false
+    id "org.jetbrains.kotlin.android" version "2.0.21" apply false
     id "io.sentry.android.gradle" version "4.11.0" apply false
 }