testing: drop castxml install from ci container build
testing: drop castxml install from ci container build

The castxml install from centos8+epel has been rather fraught with
errors including broken/failed installs and, at the time of this commit,
it installs but can not run due to llvm integration/cli issues.
On top of this it was not available on centos7 anyway and so would,
in theory, only have worked on the octopus container image.
At this point it seem that running the implements tool is not worth
all the failures that trying to install castxml causes.

Signed-off-by: John Mulligan <eda8ad33169deab44f9fe65847f99e368da6c91b@redhat.com>

ceph/go-ceph,ceph/go-ceph,ceph/go-ceph