Update to Junit 5.12.0

This updates the junit-bom to version 5.12.0 in order to get around
micrometer-metrics/micrometer#6012

Author: onobc

gradle/libs.versions.toml

@@ -18,7 +18,7 @@ assertj = "3.25.3"
 awaitility = "4.2.2"
 jacoco = "0.8.9"
 json-path = "2.9.0"
-junit = "5.10.5"
+junit = "5.12.0"
 hamcrest = "2.2"
 mockito = "5.12.0"
 spring-dep-mgmt = "1.1.7"