[Docs] Add 'only' to clarify status
[Docs] Add 'only' to clarify status

This patch adds 'only' to the implementation status
for RHEL-07-010010 to make it more clear that the tasks will take
action on CentOS/RHEL only.

Change-Id: I15b53a62817f20a09e684bdde2aaacfa02e63c17

major/openstack-ansible-security,major/openstack-ansible-security