switch2container: do not serialize the ceph-crash migration

There's no need to slow down the playbook execution time by migrating
all the `ceph-crash` instances in a serial way. Let's remove the
`serial: 1` so the migration is achieved in a parallel way.
Signed-off-by: Guillaume Abrioux <gabrioux@redhat.com>

infrastructure-playbooks/switch-from-non-containerized-to-containerized-ceph-daemons.yml

@@ -601,7 +601,6 @@
 
   vars:
     containerized_deployment: true
-  serial: 1
   become: true
   tasks:
     - name: stop non-containerized ceph-crash