no more ironic CLI commands in documentation

[Ruby Loo]

Now that we have feature parity between ironic and openstackclient (OSC) CLIs, we can update the ironic documentation to only use OSC baremetal commands, and replace any ironic commands with their OSC-related ones.

[Ruby Loo (rloo)]

I went through the documentation; we have to keep documentation for both 'openstack baremetal' and 'ironic' CLIs. Since the docs are organized by separating those two CLIs, there are no places where an 'ironic' command is being used outside of the 'ironic' CLI docs, so there is nothing to do here.