Bump kotest 5.4.0 -> 5.6.0

Author: nedtwigg

jvm/CHANGELOG.md

@@ -13,6 +13,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 ### Fixed
 - Unsupported test sources (such as `FieldSource`) no longer cause the JUnit5 runner to crash. ([#550](https://github.com/diffplug/selfie/pull/550) fixes [#549](https://github.com/diffplug/selfie/issues/549))
+### Changed
+- Bump minimum required Kotest from `5.4.0` to `5.6.0` ([#535](https://github.com/diffplug/selfie/pull/535))
+  - required to fix `java.lang.NoSuchMethodError: 'long kotlin.time.Duration$Companion.milliseconds-UwyO8pc(long)'`
 
 ## [2.5.3] - 2025-05-21
 ### Fixed

jvm/gradle.properties

@@ -9,7 +9,7 @@ ver_JUNIT_PIONEER=2.3.0
 ver_OKIO=3.16.0
 ver_KOTLIN_TEST=2.0.0
 ver_KOTLIN_SERIALIZATION=1.9.0
-# Kotest 5.4.0 is the oldest that we support
-ver_KOTEST=5.4.0
+# Kotest 5.6.0 is the oldest that we support
+ver_KOTEST=5.6.0
 
 ver_JVM_TARGET=11