[doc] Fix formatting for argument
[doc] Fix formatting for argument

Change-Id: Ifbab4ac599d2fe3dabbeebd519366d796ccdef0a

DavidPurcell/murano_temp,DavidPurcell/murano_temp,DavidPurcell/murano_temp,openstack/murano,DavidPurcell/murano_temp,openstack/murano