Update dependency io.kotest:kotest-assertions-core-jvm to v6 #99

Job	Run time
Build scip-java CLI	3m 17s
gradle-kotlin-flowext	3m 43s
gradle-java21-readiness	2m 59s
gradle-kotlin-okio	4m 25s
maven-java17-spring-boot	2m 42s
maven-kotlin-json-kotlin-maven	2m 0s
gradle-mixed-okio-jmh	3m 55s
maven-java25-demo	2m 12s
bazel-java-examples	1m 36s
	26m 49s

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