Update kotlin monorepo to v2.1.20

Author: renovate[bot]

Diff for: gradle/libs.versions.toml

@@ -14,7 +14,7 @@ mockserverClient = "5.15.0"
 org-bouncycastle = "1.80"
 org-conscrypt = "2.5.2"
 org-jetbrains-coroutines = "1.10.1"
-org-jetbrains-kotlin = "2.1.10"
+org-jetbrains-kotlin = "2.1.20"
 org-junit-jupiter = "5.12.1"
 retrofit = "2.11.0"
 startupRuntime = "1.2.0"