[doc] Update haproxy service example

With changes to haproxy role, we no longer require having
`service` key in list of services. Such defenition is considered
deprecated and should not be referenced in docs.

Change-Id: I168f75cb89580d1924bd42101d11628281426b1e

doc/source/alternate-configurations.rst

@@ -25,17 +25,16 @@ delays in case of backend failure. We need to define the following in your
    haproxy_memcached_allowlist_networks: "{{ haproxy_allowlist_networks }}"
    memcached_servers: "{{ internal_lb_vip_address ~ ':' ~ memcached_port }}"
    haproxy_extra_services:
-     - service:
-         haproxy_service_name: memcached
-         haproxy_backend_nodes: "{{ groups['memcached'] | default([]) }}"
-         haproxy_bind: "{{ [internal_lb_vip_address] }}"
-         haproxy_port: 11211
-         haproxy_balance_type: tcp
-         haproxy_balance_alg: source
-         haproxy_backend_ssl: False
-         haproxy_backend_options:
-           - tcp-check
-         haproxy_allowlist_networks: "{{ haproxy_memcached_allowlist_networks }}"
+     - haproxy_service_name: memcached
+       haproxy_backend_nodes: "{{ groups['memcached'] | default([]) }}"
+       haproxy_bind: "{{ [internal_lb_vip_address] }}"
+       haproxy_port: 11211
+       haproxy_balance_type: tcp
+       haproxy_balance_alg: source
+       haproxy_backend_ssl: False
+       haproxy_backend_options:
+         - tcp-check
+       haproxy_allowlist_networks: "{{ haproxy_memcached_allowlist_networks }}"
 
 After setting this you will need to update haproxy and all services
 configuration to use new memcached backend: