Update kotlin monorepo to v2

| datasource | package                                   | from   | to     |
| ---------- | ----------------------------------------- | ------ | ------ |
| maven      | org.jetbrains.kotlin:kotlin-stdlib-jdk8   | 1.9.21 | 2.1.21 |
| maven      | org.jetbrains.kotlin:kotlin-stdlib-common | 1.9.21 | 2.1.21 |

Author: renovate[bot]

gradle/projects.libs.versions.toml

@@ -7,7 +7,7 @@ dokka = "1.8.10"
 intellijOpenApi = "7.0.3"
 javaAssist = "3.29.2-GA"
 junit = "5.9.2"
-kotlin = "1.9.21"
+kotlin = "2.1.21"
 kotlinCompileTesting = "0.4.0"
 javaCompileTesting = "0.21.0"
 kotlinBinaryCompatibilityValidator = "0.13.0"