Fix Docker/Podman test suite image build for rocky9: add python3-devel
so 'pip3 install p4python' can compile its C extension against
Python.h. Broke after a host-level podman/OS package update on
workshop-jenkins.das.perforce.com caused the base image
(rockylinux/rockylinux:9-ubi-init) to be pulled fresh, no longer
bundling Python dev headers the way the previously-cached copy did.
Same fix already applied in //p4-sdp/dev_rebrand (change 33259).