[docs] remove deprecated ubuntu package from installation
[docs] remove deprecated ubuntu package from installation

keystone package depends already on apache2 and wsgi package:

keystone
  Depends: adduser
 |Depends: apache2
  Depends: <httpd>
    tntnet
    aolserver4-core
    aolserver4-daemon
    apache2
    ebhttpd
    lighttpd
    micro-httpd
    mini-httpd
    nginx-core
    nginx-extras
    nginx-full
    nginx-light
    webfs
    yaws
  Depends: libapache2-mod-wsgi-py3
  Depends: python3-keystone
  Depends: ssl-cert
[...]

Change-Id: I1332df34dd6ee59537d35d93d5c35c2fe96561b2
Related-Bug: #1825111

openstack/keystone,mahak/keystone,mahak/keystone,openstack/keystone,mahak/keystone,openstack/keystone