ceph.spec.in: replace golang github prometheus with promtool binary path

ceph.spec.in: replace golang github prometheus with promtool binary path

i don't see golang-github-prometheus available for centos anymore and
other distro's as well. And different package provides the promtool in
different distro's so instead of identifying all the corresponding
packages and its name, replacing the package name with binary path so it
works across distros without distro specific conditions

Some build failures are captured in our internal runs recently
https://github.com/rhcs-dashboard/ceph-dev/actions/runs/24298848427/job/70949666821

Signed-off-by: Nizamudeen A <nia@redhat.com>