Redundant javax.activation dependencies in the Maven build

PR #23890 introduced org.glassfish.jaxb:jaxb-runtime:2.3.2 as a runtime dependency. As an unexpected side effect, jakarta.activation:jakarta.activation-api:1.2.1 was also pulled in as a transitive dependency. As a result, for the Maven build, both of the following two jars can be found under assembly/target/scala-2.12/jars:

activation-1.1.1.jar
jakarta.activation-api-1.2.1.jar

Discussed this with srowen offline and we agreed that we should probably exclude the Jakarta one.