Cleanup some very old README references
Cleanup some very old README references

Private Chef and Enterprise Chef from the Chef 11 era are long gone.
opscode_org_creater was from before Chef Server 12.

A recent version of this gem should be included in all Infra Server
builds these days.

Signed-off-by: Bryan McLellan <9da9e2973b9c72b95f1bc7169993146760fceeb1@loftninjas.org>

chef/knife-ec-backup,chef/knife-ec-backup