chore(deps): update kotlin to v1.9.21

Author: pleo-bot-renovate

gradle/libs.versions.toml

@@ -7,7 +7,7 @@ guiceVersion = "5.1.0"
 jacksonVersion = "2.14.2"
 junitVersion = "5.9.3"
 kotlinGuiceVersion = "1.6.0"
-kotlinVersion = "1.8.0"
+kotlinVersion = "1.9.21"
 kotlinterGradleVersion = "3.13.0"
 logbackClassicVersion = "1.4.5"
 mockkVersion = "1.13.4"