Add jackson-core dep to MP Health TCK module to prevent elytron controlling the version

For some reason Elytron 1.17.0's dep on jackson-core 2.11.3 ends up polluting the classpath used by MP Health TCK, resulting in it being visible instead of the 2.12.3 that WF dep management declares. This results in TCK failures because jackson-core 2.11.3 is not compatible with the other 2.12.3 jackson artifacts

From looking at mvn dependency:tree output it's not clear to me how this happens, but adding an explicit dep to the MP Health TCK pom fixes the problem.