Update all dependencies to v2.1.21 (#226)

| datasource | package                                                           | from   | to     |
| ---------- | ----------------------------------------------------------------- | ------ | ------ |
| maven      | org.jetbrains.kotlin.kapt:org.jetbrains.kotlin.kapt.gradle.plugin | 2.1.20 | 2.1.21 |
| maven      | org.jetbrains.kotlin.jvm:org.jetbrains.kotlin.jvm.gradle.plugin   | 2.1.20 | 2.1.21 |
| maven      | org.jetbrains.kotlin:kotlin-gradle-plugin                         | 2.1.20 | 2.1.21 |

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

Author: renovate[bot]

libs.versions.toml

@@ -1,6 +1,6 @@
 [versions]
 jdk = "17"
-kotlin = "2.1.20"
+kotlin = "2.1.21"
 moshix = "0.30.0"
 http4k = "5.47.0.0" # Compatable with JDK 17
 immutables = "2.10.1"