ansible/podman: do not renumber at every boot

Currently, we always renumber before starting the podman service, which is:

• Only needed once, after updating the number of locks
• Suuuuuper slow, which prevented podman from starting on my farm
• Not neeeded for new farms (they will use the right values by default)

So... let's make renumbering a manual task, and we instruct people of this fact through a comment above the config line.