fix(deps): update kotlin monorepo to v2.1.21 (#358)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

gradle/libs.versions.toml

@@ -17,7 +17,7 @@ androidx-test-ext = "1.2.1"
 google-android-material = "1.12.0"
 
 jetbrains-dokka = "2.0.0"
-jetbrains-kotlin = "2.1.20"
+jetbrains-kotlin = "2.1.21"
 jetbrains-kotlinx-coroutines = "1.10.2"
 jetbrains-kotlinx-datetime = "0.6.2"
 jetbrains-kotlinx-serialization = "1.8.1"