Fix one typo in index.rst.
Fix one typo in index.rst.

Fix a one-char typo in index.rst, to regenerate and publish the docs.

Change-Id: Id8e3f1a6d231be7f9c521f41f8310252626620f1

ionutbalutoiu/ironic,NaohiroTamura/ironic,citrix-openstack-build/ironic,devananda/ironic,SauloAislan/ironic,citrix-openstack-build/ironic,dims/ironic,faizan-barmawer/openstack_ironic,pshchelo/ironic,hpproliant/ironic,Tehsmash/ironic,SauloAislan/ironic,supermari0/ironic,bacaldwell/ironic,ramineni/myironic,NaohiroTamura/ironic,redhat-openstack/ironic,varunarya10/ironic,Tan0/ironic,openstack/ironic,rackerlabs/ironic,dims/ironic,rdo-management/ironic,naototty/vagrant-lxc-ironic,naototty/vagrant-lxc-ironic,debayanray/ironic_backup,froyobin/ironic,ionutbalutoiu/ironic,bacaldwell/ironic,naterh/ironic,openstack/ironic,JioCloud/ironic,pshchelo/ironic