Ban org.javassist:javassist

Follows up QUARKUS-2208

quarkus-scheduler (supported) would require a prod javassist, but Quarkus itself does not manage javaassist.
OTOH Camel manages it but does not require a prod version. The non-prod version thus wins.
I am going to workaround this in the Platform, but the permanent fix should consist in managing javaassist in io.quarkus:quarkus-bom.

As agreed in https://github.com/quarkusio/quarkus/issues/26071 the way of fixing this in Quarkus Core is to ban javaassist and exclude it from quarkus-scheduler. This was merged already to upstream main via https://github.com/quarkusio/quarkus/pull/26069

Upstream issue https://github.com/quarkusio/quarkus/issues/26071
Upstream PR (main) https://github.com/quarkusio/quarkus/pull/26069
The PR is to be backported to 2.7