Update kotlin to v2.2.21

Author: renovate[bot]

gradle/libs.versions.toml

@@ -7,7 +7,7 @@ appstore-api = "v1.0.1"
 buf = "0.10.3"
 bundletool = "1.18.2"
 dokka = "2.0.0"
-kotlin = "2.2.20"
+kotlin = "2.2.21"
 managed-kafka-auth-login-handler = "1.0.6"
 protovalidate = "1.0.0"
 quarkus = "3.28.3"