Update kotest to v6

Author: renovate[bot]

gradle/libs.versions.toml

@@ -4,7 +4,7 @@ kotlinGradle = "1.9.25"
 
 javaDiffUtils = "4.16"
 junit = "5.13.4"
-kotest = "5.9.1"
+kotest = "6.0.0"
 kotlinx-bcv = "0.13.2"
 
 gradlePluginPublishPlugin = "1.3.1"