Update kotlin to v2.0.21 (#1008)

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

Author: renovate[bot]

gradle/libs.versions.toml

@@ -7,7 +7,7 @@ opentelemetry-android = "0.4.0-alpha"
 mockito = "5.14.1"
 junit = "5.11.2"
 spotless = "6.25.0"
-kotlin = "2.0.20"
+kotlin = "2.0.21"
 lifecycle-runtime-ktx = "2.8.6"
 activity-compose = "1.9.2"
 compose-bom = "2024.09.03"