Update dependency org.junit:junit-bom to v6

Author: renovate[bot]

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 doma = "3.11.0"
 kotlin = "2.2.20"
-junit = "5.14.0"
+junit = "6.0.0"
 spotless = "7.2.1"
 doma-codegen = "3.2.1"
 doma-compile = "4.0.2"