Remove javax.activation to fix verifyLicensing

[dagguh]

The javax.activation:activation license is not being found, for some reason.

BTW I tracked down the inclusion of javax.activation to old monorepo:

   /**
     * Necessary for JDKs, which no longer bundle java.xml.bind, e.g. Java 10.
     */
    private fun jaxb(): List<String> = listOf(
        "org.glassfish.jaxb:jaxb-runtime:2.3.0",
        "javax.activation:activation:1.1.1"
    )

Currently CI runs on Java 11, let's see if it's necessary.

[dagguh]

Welp, the CI is green. Of course there might be cases where the lack of javax.activation throws a NoClassDefFoundError. This would mean the test coverage here didn't catch it. Any bug discovered like that is a trigger to improve coverage. Better to move on than to be afraid of every change. The consumers can always revert back to the previous version.